Bifrost is a mythical bridge in Norse mythology that connects the realm of the gods, Asgard, to the world of humans, Midgard. It is often described as a rainbow bridge, symbolizing the connection between different worlds and realms. The bridge is guarded by the god Heimdall, who watches over it to prevent unwanted visitors from crossing. In the myths, Bifrost is said to be made of fire, water, and air, representing the elements that bind the universe together. It plays a crucial role in the stories of the gods, allowing them to travel between their home and the human world.