A chord is constructed from a small number of notes which, when played together, combine to give the sound of that chord. Typically, there are three or four notes in a chord, but many chord shapes on the guitar feature duplication of notes. The notes that make up a chord are sometimes called Chord Tones or Chord Notes. If we play each note of the chord individually instead of altogether in one strum, we are then playing the Arpeggio of that chord. Because the Arpeggio contains the same notes as its chord, when it is played against the chord, it sounds very musical.
The following accompaniment uses Chord Tones and will thus sound very strong over the respective chords. Play it to a standard 12 bar blues and, once you have it, play around with the notes and come up with your own 'arpeggio style riff'!