John - As a friend of mine said when I played him the A part of one tune and the B part of another and asked him the title, "You're a little confused there!"
An arpeggio is the notes of a chord played in sequence rather than simultaneously. It can be any chord (minimum of three notes) from a simple major triad to diminished sevenths or even more complex, and anything in between, not just 1-3-5. It can be played over and over for more than one octave, and ascending or descending. It comes from the Italian term for "harplike," since chords are often played that way on that instrument. You've heard it many times. There's one at the end of "Ashokan Farewell."
Next, its a musical convention to refer to the notes of the scale by Arabic numerals, and chords by Roman numerals, based on the degree of the scale on which they're based. For example, in the key of C the I chord (the tonic major triad) is composed of the notes 1,3,5 if there is no other indication added. A minor chord would add "minor" or "m," a seventh would be written as I7, and so on. Continuing in C, the IV chord is F-A-C, and the V chord is G-B-D. The IV and V chords are particularly useful because they are built on the perfect fourth and fifth of the major scale, which are basic harmonically in western music.. Any of these chords can be played as arpeggios following the above practices.
Hope this helps.

I should have mentioned that the IV and V chords are important because they are the only two triads built on the notes of the diatonic scale, in addition to the tonic, that are major chords (containing a root, major third and perfect fifth). The II, III, and VI chords are minor (a minor third and perfect fifth), and the VII triad is "diminished," with a minor third and diminished (flattened) fifth.
BTW, if you want to explore this kind of thing, I strongly suggest you get a keyboard of some kind, even a virtual one on your phone or tablet (I use Mini Piano Lite). Very useful for visualizing all this, determining keys of music, and working out passages.

Thank you for the help, Doug. Your friend was correct.
I need to read up some more. I’m confused about the relationship between arpeggios, chords, I-IV-V and what they all are in relation to each other.
I think I first have to understand what a “chord” is. Seems simple enough but need some further clarity. Will digest more what you posted.
Will follow up, and appreciate your help.

C Major scale = C,D,E,F,G,A,B,C

Cmajor Chord, (Triad, or it's three note form) = C (D, miss this out) E, (F, miss this out) G.

So C Major Triad or 3 note Chord = 1st or 1 or I chord of C Major = C, E, and G. in what is known as it's Root position,

G,C,and E in what is known as it's 2ndinversion,

And E,G,and C, in what is known as its 3rd(and rarely used) inversion.

Notes played simultaneously sound as a chord

Notes played singularly and in succession are described as an Arpeggio

Well, I got that! Thanks Pete! Especially, played together makes it a chord…..played separately, an arpeggio.

i just messed up on the names of the inversions hopefully corrected that now. rest of the triad chords built on the other notes of the scale are built exactly the same

da** it! i still got it wrong , there is no 3rd inversion just root inversion CEG, 1st inversion GCE, and second inversion EGC.

Just shows me i learn more by trying to splain something to others. Think i may be musically dyslexic

No worries. I can only take in so much at a time…??….thanks

pete - I believe C-E-G is the root position for the C major triad.
E-G-C is the 1st inversion.
G-C-E is the 2nd inversion.
At least that's what I remember. I don't know that any of them are "rarely used," at least as a pianist.
Same notes, just different order.
John - There are websites that supposedly explain music theory, but actually Wikipedia has pretty good information on all of it, although it can go off the deep end sometimes.

Thanks John, i think that the C major scale is nice for trying to explain stuff (no sharps or flats) in theory. But in practice the G,D,or A scales are the easiest to actually play. Good luck.

I can't add anything to these fine answers.
But I'll second Doug's advice of getting a keyboard app. Or a cheap keyboard. Once you get so you can identify the note names, chord theory opens up before thee. Chord Inversions and minor chords are not only before your eyes, but you'll be able to hear the difference between a major and a minor chord. Then delving into 7th, or 9th or sus, or diminished chords, etc. are revealed.

Google images of piano chord cheat sheets, both minor and major.
Google 'Nashville numbering system' eventually. Cheers!

Doug, Ahh.... i was told wrong .

i thought was told you take the highest note from the triad and put it at the bottom for the 1st inversion then repeat that for the second inversion. CEG becomes GCE for 1st inversion which becomes EGC for second inversion. but it is the opposite....told you i was musically dyslexic lol

Just shows me you can't take something as fact that some eejit like myself has told ya.

But like yo say same notes different order. Cheers

I think my big question is do the arpeggios and the I-IV-V theories have anything to do with one another?

I'm not sure I understand what your question is, but here is what I think you're asking....

The arpeggios are the notes of each chord in the key. I-IV-V theory are three of the chords in the key.

1 2 3 4 5 6 7 represents the scale of notes in a (major) key. On each note an arpeggio is built. I-II-III-IV-V-VI-VII represents the chords built on each note.

The arpeggios of each chord are

Chord (I) = the notes 1 3 5 from the scale. The (1) is the name of the chord (C) followed by an interval of a 3rd (E), and another 3rd (G). This is the pattern for every chord (triad)

Chord (III) = the notes 3 5 7.

Chord (IV) = 4 6 1.

Chord (V) = 5 7 2.

Chord (VI) = 6 1 3.

Chord (VII) = 7 2 4. 

Or, I've completely misunderstood the question.

John - I could split a few hairs here, for little purpose, but I might add that conventionally, Major chords are referred to with upper case Roman numerals, I, IV, V, and minor chords with lower case, ii,iii,vii,viii. Some people just use a lower case "m" after the numeral for the minor, but it means the same.
For practical purposes, many fiddle tunes have phrases based on scales or arpeggios, and if you recognize them it can make them easier to play. A classic example is the beginning of "Soldier's Joy" in its earlier versions:
A,F#,D,F#,A,F#,D,F#,A,D,D - see the arpeggios? Some people play this as a descending and then ascending scale, which works too, and there are other ways.
The Irish tune "Flowers of Antrim" is full of arpeggiated chords, especially the "B" part:
Here's a recording of the Critton Hollow String Band playing that tune, which I made many years ago, and still am very fond of:
youtu.be/w3oiG83Mn0M?si=hL0ytTqw6IfTSvna

Sounds to me like John was just getting mixed up with the difference between a Chord, and an Arpeggio. IE: same notes, but sounding simultaneously or in succession. Maybe?

Easy thing to do, especially if you have played a guitar before to play chord "Shapes", that can be played as a simultaneous "Chord". Or the notes can be plucked individually in succession as an "Arpeggio" using the exact same left hand chord "Shape"

It would be easy to mistakenly describe them both as a "Chord"

Thank you, all. Your follow ups are all really helpful.

Buck, when you say "Or, I've completely misunderstood the question"...... When I first posted my question, I wasn't exactly sure what I was asking (or more so, how to word it).... but via all the answers, I think I have a better idea what I was after, or at least a way to approach my confusion. ..... I did stumble on the website , musicca.com, which provides comprehensive reading on theory. A number of you mention getting a piano keyboard to grasp a better understanding of all this and the website provides a "virtual piano". It also has interactive "games" to test yourself. It's a pretty extensive learning tool. So the long and short of it.... I probably didn't really know what I was asking, but all your answers have helped a ton. Thanks very much. After first picking up the instrument a year and half ago I "think" my tone is improving (at least that's what I'm told by unbiased people... my wife). On top of learning the mechanics and technique of playing, there's learning how to read music and learning theory. Never too late, but kind of wish I started when I was a young man :-) Thanks again for all the help, really appreciate it!

At 63 (according to my wife) I still enjoy learning stuff.
And just playing tunes and maybe picking them apart to understand them theoretically. There's a reward, a peace of mind, in getting more comfortable with Music. Like any language, there may be no true ending to the journey. But, to me, it's just interesting. Cheers

As mentioned already, arpeggios are just a way of breaking a chord into individual notes played in succession versus a chord with all the notes played simultaneously. A great example of this would be the original Bach composition that was reset by Gounod into the well-known “Ave Maria” as a composition exercise. The arpeggios could be restacked into chords.

The I-IV-V progression is a different subject, as that deals with the Roman numeral chord analysis system, where I the tonic of the key and the other chords in the progression all point back to the tonic. The dominant of a key has a different root if spelled out as a simple chord, but the chord itself points back most strongly to the tonic. The I-IV-V progression is possibly the most popular progression in composition, and it shows up all over Western music.

To sum it up, the arpeggio is a broken chord spelled out and a chord progression is a series of chords that occur to form a harmonic structure for a piece of music.

Sing the do-re-mi scale in whatever key is most comfortable for your voice. Yes, "Do Re Mi Fa So (or is it Sol?) La Ti Do." When you get comfortable with this, try to sing just "Do Mi Sol." Ah yes -- the major triad! Sing 'em a lot. Get comfortable with where the pitches of the notes are as you sing 'em. You're now on your way to musical literacy -- toward getting your ears, fingers and brain into sync.

John - As Rich mentioned, arpeggios are also referred to as "broken" chords or, on piano, sometimes as "rolled" chords.
I think Pete is incorrect when he says "It would be easy to mistakenly refer to them both as chords." They ARE both chords - an arpeggio is really a type of chord - a special case if you will. The "chord" is really the somewhat abstract structure of notes. If the notes of a C chord are played simultaneously, its just a plain old chord, if sequentially it can be called an "arpeggio," but its still a C chord - same notes and harmonic structure.

Well i'm always incorrect Doug if you want to dig in far enough. Ding ding ding is an arpeggio and prang is a Chord..... lol

pete - Might be the language barrier. I thought your description was perfectly adequate, in practice (or is it practise)?

Yeah, muddying the waters is a time honored practice, but i can't spell either (or is it neither)?