Jotunheim is a cold, barren wasteland, home of the Mountain, Storm and Frost Giants and birthplace of Loki. Many battles have taken place here between the Asgardians and the Frost Giants.
In the Thor (2011) film, after Frost Giants tried to steal the "Cask of Infinite Winters" from Asgard, Thor (along with Loki, Sif, and the Warriors Three) secretly go to Jotunheim to battle them but are interrupted by Odin. Later Loki tried to destroy the realm but failed due to Thor's intervention. It appears as a planet.