Mostly hailing from Hublandia or other such mountainous areas, trolls are basically animated lumps of stone with room temperature IQs. It should be noted that troll's brains, being made of silicon, are affected by temperature. In cold areas, trolls have been known to exhibit humour, sarcasm, and even come up with a really good idea or two. In the comparative warmth of Ankh-Morpork this is unlikely to happen.
Trolls are extrememly strong and virtually unhurtable, being made of stone. They make great body guards, bouncers, and City Watch, and some enter simple trades.
Troll names are always to do with the earth, and rock formations, eg Chalky, Chrisoprase, Cliff, Detritus etc.
Trolls do have teeth made of diamond, and have occaisionly been known to crack one out and sell it. It should be noted that this is very painful for the troll, and after loosing about three teeth they are going to have trouble eating. Any Troll found selling bags of their teeth shall be sat upon by the Gods.
Speaking of eating, trolls are into gravel, potash, coal etc.
It must however be born in mind that 'troll' refers to any animate form that's close to the elements, and water trolls, though rare, are not unheard of. They are, however, rarely found on land, due to tides, and the risk of freezing or evaporating. They are long lived even by troll standards and are usually found in the sea or lakes. Many of them suffer from fish.