Here is a good explanation with a good picture: https://www.sciencefocus.com/space/what-is-a-wormhole/amp/

Unfortunately the picture shows our 3D universe as a 2D graphic folded on itself in 3D, then projected again as a 2D picture! So it could be confusing. But the movie Interstellar shows the best graphic of how a wormhole should and would work. If it exists.

If humans were to travel through the wormhole, we wouldn’t actually leave space and travel down the middle (like shown in the movie Contact) but along the surface — always touching that paper.