The Nintendo Power cartridge was an accessory released exclusively in Japan that was used for the Super Famicom and the Game Boy. With the cartridge you could download games to it, thus allowing the customer to pay a cheaper price than they would if they went out to purchase a retail version of the game. Many games were released exclusively though this system. The Nintendo Power can be considered the successor to the Famicom Disk System, whose disks were also rewritable. The Nintendo Power cartridge also solved the piracy problems that were so common with the FDS.
Players could purchase a Nintendo Power cartridge at a video game retailer. Some retailers would have stations where you could download games onto the cartridge for a small price. These places were the only places where players could place new games on the cartridges. After this, the store clerk would give the purchaser a manual of the game.