What is an arpeggio on the piano?

An arpeggio is a 'broken chord.' So on piano, if you played C,E, & G together you would have a C chord. If you wanted to arpeggiate the chord, play each note separately. You can continue this all the way up the piano: C,E,G,C,E,G,C,E,G etc. This works for any traditional chord - just play one note at a time.