A kilobyte is a collection of about 1,000 bytes.
In the metric system, kilo is 1,000, and in some cases a kilobyte is defined as 1,000 bytes. This definition is commonly used by storage medium companies and to measure data transfer speeds.
But because computers work in binary, computer scientists usually define a kilobyte as 210, or 1,024 bytes. Computer scientists used the term "kilo" because a kilobyte is close enough to 1,000 bytes.
The abbreviation for kilobyte is kB in the metric system (1,000 bytes), or KB in the binary system (1,024 bytes).
Some groups have proposed the name kibibyte for a unit of 1,024 bytes to prevent confusion. The abbreviation for kibibyte is KiB.