Wormholes do actually exist. They can be usually formed by two stars that are about to die. The dead stars will form cosmic strings, and if you travel in it through a precise angle and speed, you can actually go through a wormhole, literally.
A wormhole does not make you go faster than the speed of light. Imagine a wormhole as a folded tablecloth, you simply go through one side to the other traveling an infinitely small distance at the speed of your spaceship but you have traveled a great distance when you unfold the tablecloth.