what is inside a wormhole and what happens if you go inside it? how is it different to a black hole?

Question: what is inside a wormhole and what happens if you go inside it? how is it different to a black hole?
- Keywords:
  black hole,
  space,
  wormhole
Asked by sahil to Chris, Josh, Rebecca, Rob, Susan on 16 Jun 2015. This question was also asked by adham.
- Susan Cartwright answered on 16 Jun 2015:
  
  A wormhole is a theoretical construct that looks a bit like two black holes back to back: instead of spacetime deforming into a deep pit, as with a black hole, it makes a tunnel. In principle, travelling through a wormhole might allow you to reach a distant part of the universe in a very short time.
  
  To make a wormhole, you have to get the tunnel to stay stable instead of pinching off to make two ordinary black holes. This is difficult: theoretical wormholes require “exotic matter” with properties different from anything we observe in the universe or in our particle accelerators. So, whereas pretty much any astronomer you ask would be confident that black holes exist, it is by no means certain that wormholes do.

Question: what is inside a wormhole and what happens if you go inside it? how is it different to a black hole?