Just notes of a chord played one by one
Arpeggios are nothing more than notes of a chord played one after the other. Lots of guitarists use arpeggios to break out from scale doodling so that their solos do not sound like a series of scale exercise licks.
The arpeggios you will learn in this exercise are called triadic arpeggios because the chords you are breaking are triads. They consist of the root, the minor or major third (this determines whether it's a major or a minor chord), and the fifth.
You will notice that most of these arpeggios are just fragments of scale positions that you may already know (if not, you will very soon).