Tetromino

A tetromino, sometimes called tetramino or tetrimino, is a four-squared polyomino. The seven tetrominoes are I, O, T, S, Z, J, and L.

I
Other names include straight, stick, and long. This is the only tetromino that can make a "tetris" (four lines with one tetromino) outside of cascade games.

O
Other names include square and block.

S
Other names include inverse skew and right snake.

Z
Other names include skew and left snake.

J
Other names include gamma, inverse L, or left gun.

L
Other names include right gun.