Chord train is a simple way to explore sound, make sonic judgments, create music, and bring cohesion to a group [without too much difficulty].
We also hear these sounds commonly used.
These are so often confused, the topic got its own slide. Let's get clear on this: the G & B are 'reversed'. Middle G is line 2, 3 string open. Middle B is line 3, 2 string open. This will be valuable moving forward, again, as these two tones are commonly mistaken for each other.
With this tone set [E, G, A, B, D], play every tonal combination possible in P1. It's not infinite [though what we can do with them is]; eventually, we do run out of options. This is 'exhaustion'. We discover a bunch of resonant chords, many which are commonly used. The Em is complete [E-G-B], even Em7 [E-G-B-D]. The G triad is also complete [G-B-D]. We also find some incomplete chords. The B type chord is a 5th-less minor 7 [no f#]. The D type is a Dsus9 [no f#] - or just D5. The Am is Asus9 [no C] - or just A5. Double-stops - 2 string chords are also endlessly workable. For every string couplet there are 4 options. Example: 2 & 1 strings = 00, 03, 33, 30. Try triple-stops too - 3 string chords. We can also play triple-stops [3 string chords which may or not be complete triads]. We don't necessarily name everything we find, though we can do it. Many of the fingering possibilities manifest as changing elements, aka melodic tone toggling. While strumming a chord, we include melodic elements.