A “bit” is a basic unit of computational data. It is a binary unit, so can only ever have the values of 0 or 1.
A byte is equal to 8 bits, and corresponds with the data size of a single character (letter, number or punctuation mark) in ASCII format.
A kilobyte is 1024 or in some cases can be referred to as 1000 bytes depending on the context, but in pure technical terms, 1 KB = 1024 bytes.
For example, some manufacturers or hosting companies that deal with bandwidth or storage space may claim or calculate that 1gb is equal to 1,000 MB.
Here is a quick reference table for you
b = bit = 0 or 1
B = byte = 8 bits
kb = kilobit = 1024 bits
KB = Kilobyte = 1024 bytes
MB = Megabyte = 1024 Kilobytes
GB = Gigabyte = 1024 Megabytes
TB = Terabyte = 1024 Gigabytes
PB = Petabyte = 1024 Terabytes
EB = Exabyte = 1024 Petabytes