The term is largely a marketing hook used by dubious websites to generate ad revenue or distribute malware. While legitimate tools exist to trim file sizes slightly or manage storage more efficiently, the laws of data compression dictate that a massive open-world game cannot be squeezed into a few megabytes.
If you just want to play PS3 exclusives legally on PC, consider PlayStation Plus Premium (cloud streaming). While not a download, it requires zero storage. Ps3 Game Highly Compressed