The phrase refers to obtaining a digital copy of the Pokmon White video game, designed for the Nintendo DS, through a ROM file for use on emulators or compatible devices. These files enable users to play the game without owning the original physical cartridge. An example would be searching online for a site offering the title as a downloadable ROM.
Historically, the distribution of game ROMs has provided access to titles that may be out of print or difficult to acquire physically. This accessibility can preserve gaming experiences and allows for the play of older games on modern devices. However, acquiring and using such files often raises questions regarding copyright law and the rights of intellectual property holders.