A quick note about little-endianness

Little-endian means the least-significant byte is at the smallest address (on the left).

The least-significant byte is the byte that changes the value the least, and is in binary notation on the right:

(binary notation)

        least-significant byte
             │
          ┌──┴───┐
0b0100110110011101

The individual 8 bits that make up the byte are still in the same order. Endianness only is about the order of the bytes.

So, given the following 2 bytes:

(hexadecimal notation)

0xABCD

This would be stored in memory in little-endian as:

(little-endian)

Address: |  0x00  |  0x01
-------------------------
Value:   |  0xCD  |  0xAB

Hexadecimal notation #

One byte can store 2^8 = 256 numbers.

Hexadecimal (0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F) can store 16 numbers.

So two hexadecimal numbers (e.g. AB) can store 16 * 16 = 256 numbers, and thus one byte.

Because of this, hexadecimal notation is often used for bytes.

The prefix 0x indicates hexadecimal notation, e.g. 0xAB.