those are chords...for example Cm [x 3 5 5 4 3] Am [x 0 2 2 1 0] if ur askin abt wht chords are or how to play them then u need to check out the beginners section.. or go to this site - https://www.wholenote.com and click on 'Basics' and then check out the lessons..start from "Basic Major Chords"