Rotate
In Tetris games, the player must rotate the tetrominos, changing their orientation so that they will fit into the well in advantageous positions. Official or quasi-official Tetris games give the player the ability to rotate a tetromino either clockwise or counterclockwise as many times as the player can before it locks, with the exception of some earlier PC games which only allowed the player to rotate in one direction. All seven of the tetrominoes can be rotated, including the O piece (which has only one orientation).
If there is no space for the piece in its new orientation, it does not rotate. However, many games try to nudge the piece when rotating it against the walls of the playfield or against other blocks. These nudges are called wall kicks.