Detailed Answer -- Bits, Bytes, Kilobytes, and more...
Computers are electronic devices so they view everything as either being ON or OFF. By stringing together groups of on and off messages, computers can store and process information.
The code for ON and OFF are represented numerically as either a one (1) or a zero (0). 1=ON, 0=OFF. Individually, each one or zero is called a Binary Digit or BIT for short.
A collection of 8 BITS (or eight zeros and ones) is equal to 1 BYTE
In human terms, 1 BYTE is equal to one character (a letter, number, space, dash, etc.)
For example, when you type the letter "A" your computer sees "01000001" and if you type the letter "a" in lowercase it sees "01100001." Each zero and one by itself is a BIT; each collection of eight BITS makes up one BYTE.
1 BIT = 1 BINARY DIGIT (either a 0 or a 1)
1 BYTE = 1 CHARACTER
1,024 BYTES = 1 KILOBYTE (KB) (one typewritten page is about 2 KB)
1,024 KILOBYTES = 1 MEGABYTE (MB) (a complete novel is around 2 MB)
1,024 MEGABYTES = 1 GIGABYTE (GB) (a stack of books 60 feet high would fit in 2 GB)
1,024 GIGABYTES = 1 TERABYTE (TB) (all the books in a major research library = 2 TB)
1,024 TERABYTES = 1 PETABYTE (PB) (every book in every US library = 2 PB)
1,024 PETABYTES = 1 EXABYTE (all the words ever spoken by humans = 5 EB)