Byte
In computers, a byte is a unit of data, consisting of eight bits. All data represented on a computer are composed of them, from e-mails and pictures, to programs and data stored on a hard drive.
Technical definition
In electronics, information is determined by the toggle of two states, usually referred to as 'on' or 'off'. To represent this state, computer scientists use the values of 0 (off) and 1 (on); we refer to this value as a bit.
Each byte is made of eight bits, and can represent any number from 0 to 255. We obtain this number of possible values, which is 256 when including the 0, by raising the possible values of a bit (two) to the power of the length of a byte (eight); thus, 28 = 256 possible values in a byte.
Bytes can be used to represent a countless array of data types, from characters in a string of text, to the contents of a binary executable file. Every file is composed of them.
Sub-units
While basic, byte is not the most commonly used unit of data. Because files are normally many thousands or even billions of times larger than a byte, other terms are used to increase readability. Prefixes are added to the word byte, such as kilo for one thousand bytes, mega for one million, giga for one billion, and even tera, which is one trillion.