Wikipedia
The Retrode is a USB adapter for legacy video games that enabled the use of game cartridges and controllers with emulators. Technically, the Retrode could be considered a ROM dumper in that it could create a copy of the cartridge content. Unlike most such devices, the Retrode could be operated without drivers or special software under the most popular operating systems. It further allowed the emulator to directly access the game data through the file system, eliminating the need to create a ROM image as a separate step. By default, the Retrode was equipped with cartridge slots and controller ports for the SNES and Sega Genesis (also known as Mega Drive) systems; support for cartridges and controllers for other systems could be added via so-called plug-in adapters that you can buy online or make yourself.