GMod maps have prefixes. Nobody ever understands them anymore.

also guide needs more map types because plz

Sandbox maps. Probably the most common map type on the workshop. Basically no generic guidelines at all. You have no idea what to expect when you're loading one of these up, though you can generally assume there won't be too much railroading. Labeled "Sandbox" in the map select.

Maps intended for Trouble in Terrorist Town. Small, with lots and lots of detail. Hidden passages and breakables, lots of spawn points for TTT items and such. Good for running around in with friends.

Sort of like sandbox, but intended for GMod roleplay. Minimalistic in interactiveness, but most of the time you'll at least be able to waltz around in the buildings. Some of these maps are just absolutely lush with detail.

Deathrun maps, designed for deathrun. One person operates the deathrun while others run through it. Useless for SP.

Maps designed for physics experiments, where many components are actual, physical objects. A good CPU is essential for playing around with these maps. Enabling multicore wouldn't hurt either.

Prop Hunt, for the Prop Hunt gamemode, where you possess props and hide from people. Also likely to be dense, like ttt_ maps.

An intangible dome that distorts as you approach its edges, with a fancy picture inside. Really only useful for screenshots.

Spacebuild for spacebuild. Unless in the spacebuild gamemode, you'll be able to just fly about in any old vehicle normally without dying. You can even fly around in a helicopter from WAC or Neurotec (god rest its soul).

For a gamemode called Stop it, Slender. Just a map in Sandbox mode, or any mode but Stop It, Slender. In this gamemode, one Slender chases around a bunch of people. Spooky, probably?

Zombie Survival, where characters fight an endless zombie wave. When a character is killed, they respawn as a zombie and get to join the fun on the enemy side.

Deathmatch. Designed for players to beat the snot out of each other, Quake-style.

Maps that were created by people who either couldn't find a fitting prefix or were simply too lazy to find a matching prefix.