When I was 13, it was easy if a little redundant.
100gs, 200gs, 300lx, 400lx, 500lx, DeoreLX, DeoreDX, DeoreXT, and finally, XTR.
DX turned red and downhill, then disappeared I think.
100-300 basically became Alivio.
400-500 became STX which later became Deore
LX stayed LX for a long time and I think actually went to SLX
XT and XTR stayed put but XT got a lot less racy and more toury for a while. Then back.
Anymore, both in weight and function, SLX and XT might as well be the same.