Your first question is what's a wormhole. If you're not a sci-fi fan, then the best way to describe it, is a tunnel which connects two different spaces. Think of it as the door-frame to your house. On one side of the door is the outside, and on the other is the inside. Travel through the door and you can move between the to places. Now put that "door-frame" between two universes, and suddenly you have instant access to travel between them.
Or atleast that's what I got out of the show.
One way is the Multiverse theory. This theory, proposed by David Deutsch, indicates that there exists a universe for every possibility. Every time an event could have more than one outcome there is a universe created for each outcome. In our universe a meteorite caused the extinction of the dinosaurs. A parallel universe exists in which the meteorite missed Earth, and possibly several others in which the meteorite struck another planet or was not formed at all. In a parallel universe Hitler did not invade Russia and consequently won the Second World War. In yet another, Elvis is still alive.
But could it be possible that they are real? 58% of physicists, including Hawkins says yes. 18%, including some British nut named Roger Penrose, says no. 11% don't know, and frankly don't care. But, as an American the true test of whether we should believe something is if Einstein thought it was real. For Americans Einstein is the benchmark by which we measure the validity of scientific data. Einstein along with some guy named Nathan Rosen suggested that black holes, and their counterparts the "good" white holes, would pair to form a vortex wormhole. You may have actually heard this phenomenon before referred to as the Einstein-Rosen bridge. The idea is that all the matter is sucked up like a run away hoover into a black hole, doesn't disappear, but is shot out it's bum somewhere else; perhaps an alternate universe.
So somewhere out there in space and time, there could be another Daily Planet, another me, living a different life. Maybe in another universe, I'm rich, skinny and can actually spell. No really it could be possible. The question is how do I transverse this wormhole to where skinny Liv is, kill her, and take her place? You can't yet. Supposedly going through a black-hole hurts a little, or atleast we think it does:
What happens to you if you fall into a black hole?
In a blackhole, I won't, before I fall in, be able to see anything within the event horizon. But there's nothing locally special about the event horizon; when I get there it won't seem like a particularly unusual place, except that I will see strange optical distortions of the sky around me from all the bending of light that goes on. But as soon as I fall through, I'm doomed. I have to hit the singularity eventually, and before I get there there will be enormous tidal forces-- forces due to the curvature of space-time-- which will squash me in some directions and stretch them in another until I look like a piece of spaghetti. At the singularity all of present physics is mute as to what will happen, but I won't care. I'll be dead.
Of course that's the "bad outcome" of the "choose your own adventure: wormhole edition", and the truth is we really don't know what happens when you jump in that wormhole. Until someone volunteers, and we can find one then the best we can do, is guess. Some people even think the Bermuda triangle may be a wormhole through the Earth that leads to a similar spot on the other side of the earth.
The truth of the matter as soon as America accomplishes transversing a stable wormhole, somehow Republican's will find a way to make money off of it, and some how Delta Airlines will still have layovers in Atlanta.... and that's a fact.