When I Turn Switch Nothing Happens. Lights And Horn Works Fine.what's Wrong?

It takes a lot more voltage to crank the engine than it does to blow the horn or turn on the lights.
Could be a loose connection or corrosion on the battery cables, but is more likely you need a new battery. You can take it out of the vehicle and have it load tested to find out if that is the problem.

Try turning your lights on and starting your car, if your lights cut off or go really dim, you have a bad battery or loose connection, if it make sure your in park, if that does not help. Try putting it in neutral, it could be neutral safety switch is bad.. Try to jump start it. See if you have a alarm light flashing on dash if it has one, could cause problem.. Your starter could also be drawing to many amps, which it would still click..put a volt meter on battery and see if you have 12 volts...alot of things to check...