A bit (short for Binary Data digit) is the smallest unit of data in a computer. It can hold only one of two values: 0 or 1, representing two physical states such as off/on, low/high voltage, or false/true.
All digital information—text, images, sound, programs—is built from sequences of bits. In hardware, bits are stored as electrical signals in memory, magnetic orientations on hard drives, or pits and flat areas on optical discs.
Eight bits grouped together form a Byte, which can represent 256 different values (from 0 to 255). While storage capacity is measured in bytes (B), data transfer speeds (like internet bandwidth) are often given in bits per second (bps).