No.1 is a typical James Taylor style chord progression - the chords are fingerpicked, and rather than using all the possible notes of the chord, are stripped down to the essentials - which means they sound great. The 0 symbol means open string, the X means don't play this string. Note that the chord name is not exact, but it can be used as a substitute chord in this key.

No.2 is a harmonised scale in D, with added 7ths in each chord. Notice how chords 2,3 and 6 in the sequence are the same shape, a minor 7 shape. Admittedly, they are tricky to play.

A suggested fingering: first finger half-barre, then second finger does a partial barre on the top 2 strings. It's not as bad as it sounds. You could try your own fingering too.

No.3 is moving chords over a D bass note (open string 4)

Finally, No.4 gives you one way of playing a D major scale, and Bm pentatonic.

I've missed out a note on the diagram - fret 7 on string 2 should be there too. Both scales can be used to improvise with all the chords given here, or play the melody line in this key. Bm is the relative minor key to D, so they share most of the same notes and are strongly related. In the same way, Am is strongly related to C major, and all the same patterns work, just down 2 frets.

I'll describe the sequence in No.2 as a root 4 chord progression, meaning the root note of each chord is on string 4. There are also root 5 and root 6 scales, which I've covered in my earlier hubs.

If you look at the bass note for each chord, they are all built on the notes of a D major scale -

D E F sharp G A B C sharp D.

Once you have learned the pattern quite well, you can move to other keys - for instance (with a little adjustment to the first chord), up one fret would be Eb, up 2 frets would be E, up three frets would be F, and so on.

JS Bach thought the key of D was the voice of God. It's certainly a very guitar-friendly key. You can increase the bass response of your guitar by tuning string 6 down to D.