So, first we need to know how to count; no, this is not a joke, because you really do need to count, in more than just decimal. Here's what you need to know.
Binary: Base 2, only uses the numbers 1 and 0 It goes like this:
You only really need to know binary up to 11111111 which is the same as 255
Secondly, you need to know Decimal, which is what you have been using since you were born. Base 10, uses 0 - 9 as numbers.
You will also need to know Hexadecimal: Base 16, uses 0 - F as numbers.
0 - 9
0 - 9
You will need to know this up to FF Which is the same as 255
So now you know that, we can learn what a byte is. Each box in a hex editor is one byte. A byte is made up of 8 bits, each bit is a binary digit. So an 8-bit code is a 1 byte code, similarly, a 16-bit code is a 2 byte code. Each byte is 8 Binary digits long, 3 Decimal digits long, and 2 Hexadecimal digits long. For example:
I hope you find this useful, and that it explained some things to you you might not have known before.