Binary
Base 2. 0’s and 1’s. Binary is how all computers store and deal with data, whether that data is representing numbers, words, images, audio, video, etc. Each 0 or 1 in a computer is known as a bit. Eight bits make a byte. Each byte can represent upto 255 as a decimal. However each byte can represent 256 numbers as it includes zero: 0-255 = 256 numbers.
Example:
Video to follow.
Decimal
Base 10, no need for more detail, this is your everyday mathematics.
Hexadecimal
Base 16 – 0 1 2 3 4 5 6 7 8 9 A B C D E F