The word "arpeggio" comes from the Italian for "play upon the harp," hence its use to describe a chord broken up into a quick succession of notes, as you would strum harp strings. In sheet music for piano, a wavy vertical line indicates an arpeggiated chord, in which the pianist plays each note in turn, rather than all the notes at the same time. Playing an arpeggiated chord requires practice as you get used to combining the fast pace with the equal spacing of notes.
Play an Arpeggiated Chord from Sheet Music
Place the fingers of your left hand over the left-hand notes of the chord -- those on the bass stave, unless otherwise indicated. If the spacing is too wide, hold your fingers in position over however many of the notes you can comfortably cover.
Place the fingers of your right hand over the right-hand notes.
Play the notes of the chord from left to right, holding down the sustain pedal. Make the notes of exactly equal length.
Play the notes again, but faster, still holding the sustain pedal and keeping the note lengths even. Speed up as you get used to the notes.
Play the notes in the same way, but at rapid speed for the final effect. The exact speed will depend on the style and tempo of the piece, as well as your own style and preference.
Arpeggiate a Chord
Place the little finger of your left hand over the root note of the chord. In a C major chord, for example, place your little finger over the C.
Place the middle finger and thumb over the third and fifth of the chord. In C, these would be E and G.
Place the fingers of your right hand over the root, third, fifth and octave. In C, for example: C, E, G, C.
Play all the notes from left to right in quick succession, holding down the sustain pedal. Make all the notes of equal value.
Play several times, speeding up each time until you reach the desired speed.
If you wish to play a descending arpeggio, simply follow the same steps, but reverse the order of notes when you reach the top. For example: (ascending) C, E, G, C, E, G, C, (descending) G, E, C, G, E, C.