In the world of PC gaming, a "repack" is a version of a game that has been modified, usually by a third-party group, to make the installation file smaller and more convenient to download. The original game files are compressed and sometimes stripped of unnecessary content (like extra language packs). A repack typically includes a crack to bypass the game's official DRM (Digital Rights Management), allowing the game to be played without a purchase.
The FIFA 15 Sharahi repack is particularly popular because it offers:
Unofficial repacks hosted on third-party forums or peer-to-peer networks carry inherent security risks. Disreputable hosts often bundle adware, miners, or malware into old installers.