It is a game that was originally a mod of Half-Life 2, hence the name Garry's Mod, until it eventually grew enough to become its own game. It has no real objective other than to goof off, and is a game that I've always found interesting even as a kid mostly through VanossGaming videos.
Due to it being built on the Source Engine, and pretty much all of its assets being from Half-Life 2, it can have a sort of tarnished, run-down feel that contrasts the silly nature of the game pretty heavily.
oh hi yotsuba :)
Honestly, while I do love playing Gmod with my friends and messing around, my favorite part has always been just exploring maps and looking around at what people have made (which I usually do by myself.)
Pretty early on into the Pandemic lockdown, I got really into playing Gmod by myself to combat the boredom of having not much else to do. I'd just download and play every interesting looking map I could find, listening to music, while everyone else was asleep.
There's just something about the atmosphere of the game that feels different from any other I've played. It can switch from unnerving to comforting at any time, although I'm usually too busy admiring the architecture of whatever map I'm playing to really get spooked or anything (bleghhh gmod arg oh my god aaahh liminal space)
Click on the text to the left to see what more I have to say about the game, from screenshots, fav maps, gmod youtubers I like, and even a gmod mapping tutorial if you're interested.