my guess would be that they means true or false, there are no global booleans in C2 (oversight IIRC) so people use generally 0 and 1 to represent it. for exemple pause = 0 could mean the game is not paused, and pause= 1 means the game is paused.
however, 1 or 0 are just a choice, it could be -1 and 1, or 0 and 2, that would work too in theory.
just my thinking of it.
also in conditionnal expressions, 0 means false and every other number seems to mean true, so there is possibly that too.