Ever come across a large Snorp-looking boulder, sitting in sunlight? Chances are it's a petrified troll, so you might wanna camp out elsewhere. Once the sun goes down, the troll is going to wake up.
Trolls vary in shape and size, and may have wildly varied proportions. They're much larger than humans, have patches of fur (hair...?), and a tail. Generally they look like a caricature of your 60 year old off-putting and disheveled uncle with like 20 mental illnesses and a lot of poor life choices...
Trolls, on the other hand, can't be good guys. Or, well, maybe? *scratches head* Fuck, who am I to say what's good and what's evil, but...
As fae, they're innate tricksters with a really sick sense of humor, and they will have fun on the expense of the people they come across. As with all fae, they follow their own rules and logic, so you can't really reason with them.