A binary digit, also known as a bit, is a single unit of information used in computing. It is represented by either a 0 or a 1, and is the smallest unit of data that can be processed by a computer. The term 'binary digit' is derived from the fact that it is composed of two distinct digits, 0 and 1. In computing, these two digits are used to represent all possible values, making them the foundation of digital technology.