Endianness refers to the direction in which bytes are transmitted over a data communication method.
Big-endian works by transmitting / storing the most significant byte first.
Little-endian works by transmitting / storing the least significant byte first.
Consider the number 0x12345678 if we were to write this to memory at the index
| Value | Address |
|---|---|
| 0x12 | i |
| 0x34 | i+1 |
| 0x56 | i+2 |
| 0x78 | i+3 |
| Value | Address |
|---|---|
| 0x78 | i |
| 0x56 | i+1 |
| 0x34 | i+2 |
| 0x12 | i+3 |
Notice how in both the actual order of bits in the individual bytes is unchanged.