There are two units of memory: - a) Bit or Binary and b) Byte.

BIT- BIT is a short form of Binary Digit. One bit expresses a 1 or 0 in a binary digit.
BYTE- A Byte consists of 8 Bits. A Byte can represent a single character, such as a letter, a digit or a punctuation mark.
1 Character = 1byte = 8bits
1 Kilobyte (KB)      = 1024bytes
1Megabyte (MB)    = 1024kilobytes
1 Gigabyte (GB)     = 1024megabytes
1 Terabyte (TB)      = 1024 Gigabytes
1 Petabyte (PB)       = 1024 Terabytes
1 Exabyte (EB)        = 1024 Petabytes
1 Zettabyte (ZB)      = 1024 Exabytes
1 Yettabyte (YB)     = 1024 Zettabyte

NOTE: - Each 1 and 0 is known as ‘binary digit’ or a ‘bit’.