So I see there is the Hd Mod Category. Recently I've been playing the GoG Version of Diablo. Is that what the HD Mod refers to? Because there is a mod called belzebub but it's also referred to as "hd mod" so I'm not sure.

Heyo. GoG version is still the standard version of Diablo. Regarding HD Mod, I think it's belzebub mod. There is a Tchernobog mod as well and frankly I'm not sure which one is "the HD Mod" listed in these categories.