Byte

An amount of disk space, or computer memory, able to store eight bits of information. Since it usually takes eight bits to store a single letter of the alphabet or punctuation mark, a byte is often called a "character". 

When used to store numbers, a single byte can store any value between 0 and 255, or between -128 and +127 (if signed numbers must be considered).

Computers usually contain several million bytes of memory, and several billion bytes of disk space. One million bytes is often called a megabyte (abbreviated "MB"), while a billion bytes is called a gigabyte (abbreviated "GB").