Options menu

Preferences
Allows you to change the main game options, see User preferences.

Pause/Unpause game
This will pause the game, whilst the game is paused you will not be able to see any pictures on the tiles.

Background manager
This allows you to select a background, see the Background manager.

Undo last move/shuffle
Selecting this will take back the last move you performed, i.e the last 2 tiles you matched will re-appear where they were. You can take back as many moves or shuffles as you like, there is no limit.

Redo last move/shuffle
This will redo the last move which you took back, i.e if you just performed an undo, then this will redo that move.