Generations are an even more generalized GOL-like automata where besides the survival (S) and birth (B) rules, you are also free to pick the number of states (C) a cell can go through, which in standard Life is 2.
Couple that with additional modifiers and you have a very powerful editor that can do way more than you could ever imagine.
Here's what 20 states look like, for example.
The colorschemes are very pretty.