its just G major but a different voicing.
G major means any combination of the notes G B D.
when you play a "normal" G chord you get the following combination
E 3 = G
A 2 = B
D 0 = D
G 0 = G
B 0 = B
E 3 = G
so the total set of notes is G B D G B G
you have G B D with extras of G and B
if you only play the bottom 4 notes:
E 3 = G
A 2 = B
D 0 = D
G 0 = G
you still get G B D G
still the same notes, but less extras.
with chord symbols, all you write is "G", because players get to choose which voicing.
they could even choose to play a G barred chord
E 3 = G
A 5 = D
D 5 = G
G 4 = B
B 3 = D
E 3 = G
yielding GDGBDG
still just GBD but in a different order with different extras.
if you want to specify exactly what notes to play, you have to use normal notation or tablature.
symbols are not that specific.