What is the relation between that a kilo byte1024 bytes?

Simply it is down to mathematical powers of 2. Computer memory is based on the binary system, which is a base 2 number system. If you keep doubling 2 you get the following numbers.

2

4

8

16

32

64

128

256

1024.

All of these numbers occur regularly in computers, as do numbers after those if you keep doubling up. For example there are 8 bits in a byte; there was a computer called the Commodore 64; you hear about 256MB of RAM. There are many other examples.