Trolls and ogres are the mythical giants of northern European folk tales, especially those written or collected in the 19th century. They do resemble Norse Jotun in some ways, but their appearance and attributes are more varied. Some tales depict them as cannibalistic, others are more dwarf like creatures. Some trolls, like some dark elves, turn to stone when the sun shines on them. They inhabit the outer reaches of Asgard, Midgard, Alfheim, Jotunheim and Svartalfheim.
The whole world was created from the corpse of the first Jotun, named Ymir. Ymir was killed by the Gods Odin, Ve and Vili. They formed Jotunheim mostly from rocks, snow and dense forests, so the giants lived from the fish in the rivers and the animals in the forest, because there was no fertile land in Jotunheim.
In Norse mythology, Thrym was king of the Giants. In one legend, he stole Mjollnir, Thor's hammer, to extort the Gods into giving him Freya as his wife. Thor, son of Odin, later killed Thrym, his sister, and all of his jotun kin. (this is an interesting tale of Thor in a brides dress and cunning behavior of Loki it you want to look more into it: Thor's Wedding Day)
The jotun are an ancient race, being the first beings created, they carry wisdom from bygone times. But they are also the end of the world. In Norse mythology, jotun inflict the final destruction of the world by setting fire to the world at the end of Ragnarok, when the jotun launch an attack on the Gods and kill all but a few of them.
Jotunheimen is a mountainous area of roughly 3,500 km in southern Norway and is part of the long range known as the Scandinavian Mountains. The 29 highest mountains in Norway are all in Jotunheimen.