wormhole

The term wormhole refers to a (theorized) connection between two regions of space, presumed to be curved space, as per general relativity (GR), other than via the usual space between them. It constitutes a different route between two regions than the normal route, which could be shorter or longer than the normal route.

A two-dimensional analog is a torus surface (i.e., doughnut shaped surface, as opposed to a plane or a spherical shape): there are locations on the torus surface where a curved looping line along the surface could go all the way around you, yet there exists a way along the torus surface to a point on the other side of the line without crossing the line. A wormhole is analogous to this but in three dimensions.

No actual wormholes in the universe are known and they are generally thought to be non-existent or are part of extremely exotic situations that we don't commonly encounter, but though a universally flat (Euclidean) space would preclude them, the fact that space is curved encourages theorizing. There are multiple theories of actual wormhole possibilities, based on general relativity or similar theories. A Schwarzschild wormhole (or Schwarzschild throat) and an Einstein-Rosen bridge are two such theorized types. Despite the reference to travel through a wormhole in the description above, for some wormhole-theories this would be impossible, e.g., the presence of your mass within it would make it collapse before you could possibly get through.