This exercise will help you gain better control when moving through strings with your motor (right) hand.
Fingerpicking has some advantages over any other technique, it alows you to simultaneously pluck multiple strings at once, you can move between strings a lot faster than you could with alternate picking (e.g. for playing arpeggios), you can develop your dynamics to be better controlled than with picking and so on.
This exercise is designed to help you gain better control for shifting between strings. Since it is an intermediate lesson, only three motor fingers are used for plucking.
I hope that you will find this lesson inspiring for generating your own ideas as well.