This is the Life simulation, it is based on Conway's Game of Life. This does not actually include his rules, but if you want to look the game up on Yahoo, it's quite interesting.
There is a grid of squares, each either occupied or not (white is not occupied). The grid is started with a specific pattern which is designated by the first drop-down menu.
Then in each subsequent turn, there is a specific rule that each square looks at. If that condition is met, that square becomes occupied, otherwise, the square becomes, or stays, vacant. The rule is determined by the second drop-down menu.
The colored option makes it so that the longer a square is occupied, the darker its color becomes. A square that just became occupied is yellow, while one that has been occupied for the longest time becomes black. Without coloring, squares are either black (occupied) or white (not occupied).
You can play around with the grid size and see what happens. Try making the dimensions odd or making one side longer than the other.
Have fun!