Focus: This is usually the first step for a beginner. With this information you will be able write and play hit songs, create beautiful acoustic arrangements, or record strong backings for your solos.
There's only one barre chord to play in this one, the B minor, so it's an easy enough one to pick up for beginners. Most of the time you won't hear the m7b5 chord being used in songs as it isn't a very strong sounding chord.
D is a very popular guitar key with simple-to-add D embellishments such as and D sus2 (used in the outro) and Sus4 (covered later). Contains two barre chords.
The key of F is not used as often for guitar because it has a lot of barre chords and not a lot of ringing open string ones. It can be a difficult key for beginners uncomfortable with barre chords.
A is a very popular guitar key with the 3 main chords A D E - which are easy to play, and all feature the open strings. This gives the key a very full sound on the guitar.
There's more songs out there in A than you can shake a stick!