generation:
shows how many generations the pattern advanced

undo:
shows the number of undo states, that is how many patterns are saved on the undo stack

redo:
the number of redo states, that is how many patterns are saved on the redo stack

mode:
p is showed when pan mode is on.
d is showed when the drop selection before running option is checked.
t is showed when the table tool shows the next generation.
x is showed when xor mode is on.

state:
show what state is selected

tool:
shows what tool is selected

board size:
shows the size of the board

pop count:
show how many cells there are in the current pattern