A "bit" is the short name for a "binary digit" that can have only two values: 0 or 1.
1 byte is usually defined as 8 bits.
1024 bytes = 1 kilobyte
1024 kilobytes = 1 megabyte
1024 megabytes = 1 gigabyte
Note:
All the above definitions have long been in common everyday usage within the computer industry.