They upload gog installers for games. Gog (good old games) is a game storefront that doesn't have any drm, so the installers you download off this website are identical to what you'd get if you paid, cryptographicaly signed and everything. Because they don't have any drm to check if you own the game or not, they work without any modification.
Because gog has a strict no drm policy, most AAA game publishers don't put their games on gog, but there are some. The big focus is indie games though. If nothing else, I like to try before I buy.
I hope this explanation makes some sense, I am very tired.
depends on what you like, but evergreen stuff is the most recent triple ayyyyy offerings, like Dad of War is there, the witcherinoos, Cyberpunk 2077 and the dlc.
Warcraft 1 and 2 are there too, all the old Black Isle/Bioware crpgs.
Bethesdas good games (Morrowind and Daggerfall, Fallout New Vegas) and uuhh...i dunno Empire Earth?
STAR WARS™ Galactic Battlegrounds is like Age of Empires 2, but Star Wars.
Deus Ex & VTMB.
Master of Orion 2 hold up very well in the space 4x genre.
Dungeons & Dragons: Dragonshard is like a Warcraft 3, but it's Eberron setting and the large armies turn into single dudes when you go underground to do dungeon dwelling, it's pretty unique.
Speaking of unique there's Original War, which is a great rts that no one except me played.
oh shit! almost forgot, get all the old LucasArts point & click games (Sam & Max Hit the Road, Indiana Jones and the fate of Atlantis and Maniacs Mansion at the very least)
I've been playing a lot more puzzle games recently, I also really like adventure and rougelike games. I also like platformers. The only kind of game I'm probably not going to play is an rts/tbs (only because I already have favorites of those).
kenshi, nightmare reaper, dex, mount and blade warband/bannerlord, grim dawn, divinity original sin 2, baldur's gate 3, project zomboid, barony, disco elysium, partisans 1941