Bit

Wikipedia also has an article about Bit.

A bit is a single base-2 integer representing either the value 'ON' (1) or 'OFF' (0) In the Pokémon games, the simple concept of an ON and OFF value is useful for binary switches, for example whether the player has received the Pal Pad (ON) or not (OFF).

An ordered collection of bits (usually 8) is commonly known as a byte.