The DYI Gmod2 / Magic Desk cartridge is a cartridge that is compatible to the well known Gmod2, Ocean or Magic Desk type cartridges, for the Commodore 64... and Commodore 128 as well.
A lot of Commodore software is still being written today and nowaday, often designed for cartridges. A bank switched cartridge offers a rather large amount of storage that is instantly available without loading, and also directly adressable, which means the Commodore 64 can execute code directly from cartridge. Games can access large amounts of graphics data, which was a lot harder with floppy disks in the golden days of the Commodore 64, let alone tapes. As a result content rich C64 games are being made, which is a new chapter in the already rich software catalog of the Commodore 64.
Popular formats in mass produced C64 cartridges are Magic Desk, Ocean and nowadays, Gmod2. This item is a DYI it that allows you to build these cartridges, but unlike the mass-produced cartrdiges, this cartridge is not designed for mass production purposes, but is rather aimed at hobbyists and developers.