Jotunheim is an alien world populated by a species known as Frost Giants in the Marvel Cinematic Universe. The climate is extremely cold, and the world is covered in glaciers. All life on Jotunheim is adapted to the frigid conditions. Jotunheim may not be in the same universe as Earth, as the laws of physics there appear to be significantly different from ours.
Frost Giants are blue-skinned humanoids who stand about fifteen feet (five meters) tall. Even for their size, they are strong and durable: Frost Giants can easily lift thousands of pounds and resist fire from modern firearms. They can tolerate extremely low temperatures, and they can suck the heat out of anything they touch. They can also create weapons out of ice at will. Like the Asgardians, they have very long lifespans. They may have superhuman senses, as Loki was able to detect an arrow fired at him from a composite bow in time to catch it.
The Frost Giants appear to have a monarchal government. The last known ruler was Laufey. Their current ruler is unknown.
The Frost Giants have no known fleets or other means of interstellar travel. They once possessed a weapon, the Casket of Ancient Winters, that could create rays of extreme cold. They were also capable of interstellar/intergalactic teleportation, although they apparently lost that capability when they lost the Casket to the Asgardians. They typically engage their enemies in close combat, although they can fling sharp shards of ice with enough force to injure Asgardians. Some Frost Giants can manipulate much greater masses of ice with their thoughts.
They do not appear to pose a major threat to other civilizations at present, but other civilizations might find invading Jotunheim problematic.