Endianness or byte order is the order of bytes in a multi-byte value like a word. Systems are usually referred to as either 'little endian', where the least significant byte (lsb) comes first, or 'big endian', where the most significant byte (msb) comes first.
More non-ROM hacking specific information can be found at Wikipedia's Endianness article.
Little endian systems
- Nintendo Entertainment System
- Super Nintendo
- Nintendo Game Boy
- Nintendo Game Boy Advance
- Nintendo DS
Big endian systems
- Sega Genesis
- Many Internet protocols, such as TCP.