The Sega Genesis, also known as the Sega Mega Drive, was a video game console based on the Motorola 68000 processor. It used ROM cartridges for gameplay.
Main article: Sega Genesis:Hardware information
Sega Genesis ROM images generally have the extension .BIN, although some ROMs are in a different format, such as the Super Magic Drive ROM format (.SMD). These formats are harder to hack because of swapped bytes and other changes, so they should be converted to the normal binary format (.BIN) before you try to hack them.