Alfheim is one of the Nine Realms and the home of the Light Elves.
During the Convergence in the distant past, the Nine Realms aligned and the borders between worlds became blurred. One of the worlds in the Convergence was Alfheim.
After the destruction of the Rainbow Bridge, the Nine Realms, including Alfheim, were left vulnerable to attack without Asgardian protection.
When the Convergence occurred again in 2013, Alfheim once again became aligned with the other Realms.