Asgard is one of the Nine Realms.
After Thor touched a cursed amulet around a Frost Giant's neck, Spider-Man and his team decided to help him and so he took them to Asgard. When they arrived, they found the realm covered in ice. Frost Giants captured them, and then they found themselves confronted by Loki himself, who revealed his plans to kill Odin and usurp the throne. After a fight, Thor realized they would not win the fight and transported them out of the castle.
Soon after, just as Loki was about to open the doors that led to where Odin was resting, Thor, Spider-Man, and his team arrived once more with weapons that had been given to them by the dwarf blacksmith Eitri. After a battle with the Frost Giants, the heroes confronted Loki. They were able to defeat Loki and save Asgard from coming under his rule. Afterward, Thor returned the heroes to Earth and returned once more to Asgard.