This is a video heavily based on music theory principles.
To fully understand this video, you should know basic theory.
Notes in music: A A# B C C# D D# E F F# G G#
Major Scale Formula: W W H W W W H
C Major Scale: C D E F G A B C
C Major Scale Chords: C Dm Em F G Am Bdim
Here is a great resource I use often for teaching my students basic music theory: http://www.guitar-chords.org.uk/chords-key-c.html
To understand how I was playing the chords and choosing strum patterns, look into my eBook How To Play Any Song on Guitar here: https://www.amazon.com/dp/B01BCOGXJY/ref=cm_sw_su_dp