This is a predicted tunnel connecting two points in space and time. It is also called an Einstein-Rosen bridge, after the two scientists who came up with the idea. But for now, wormholes are still just an idea. No scientist has ever observed one.
In a sentence
When the astronauts travel through a wormhole in the movie Interstellar, they are traveling through something scientists have never seen.
wormhole A tunnel or bridge that would allow objects to take a shortcut path between two distant places in space and time. Although none has yet been witnessed, Einstein’s theory of general relativity predicted that they could exist.