A chord, in music, is any harmonic set of pitches consisting of multiple notes that are heard as if sounding simultaneously. For many practical and theoretical purposes, arpeggios and broken chords, or sequences of chord tones, may also be considered as chords.
An arpeggio is a type of broken chord. Other types of broken chords play chord notes out of sequence or more than one note but less than the full chord simultaneously. Arpeggios can rise or fall for more than one octave. Students of musical instruments and singers learn how to play and sing scales and arpeggios.