My belt actually snapped and got caught up around the crankshaft pulley and now it wont start, it just keeps on winding over and thats it. what is that sensor that sits at the top of the pulley and could it matbe have been broken by the belt.

That sensor is the crankshaft position sensor. Its used to tell the engine when to fire the spark, and could have been damaged.

Might be easy to wander down to a wrecker and get a replacement to try. You might also be able to pull the codes from the computer. It might have a code for a dead sensor which would help pin point things quickly.