A Tetris piece is composed of four squares arranged in various shapes, and is made up of the words 'BLOCK', 'ELL' and 'TEE'. The word 'BLOCK' is a five-letter word that refers to a solid, three-dimensional object with flat surfaces. The word 'ELL' is a three-letter word that is used to refer to a shape resembling the letter L. Finally, the word 'TEE' is also a three-letter word that is used to refer to a shape resembling the letter T. Together, these three words form the term 'Tetris Piece'.