One byte contains two nibbles. Each nibble contains four bits. Each of these three terms refers to a certain number of digits in binary code.
Binary code, the language of computers, is written in ones and zeros. The ones and zeros tell the computer which transistors to turn on, represented by one, and which to turn off, represented by zero. Text and numbers, for instance, can be broken down to binary code. Therefore, a bit represents one of these digits of binary code, such as "1." A nibble, on the other hand, represents four of these digits, such as "1011." Consequently, a byte is eight of these digits, such as "10111010."