Chord sequence
Am7 D7 Em7
In every key
Four-note rootless voicings in their two forms, with the 3rd or the 7th on the bottom, played over the root.
Heard in G major
All the chords
A ii-V that lands on vi instead of I: the harmony sidesteps to the relative minor where the ear expects the tonic.
Over Am7 · ii7
Mode 2 of Major
Over D7 · V7
Mode 5 of Major
Over Em7 · vi7
Mode 6 of Major