Q: Car clicks and doesn't start.

Even though it just clicks the battery can still be the problem. Low battery voltage wont have enough juice to turn the starter all the way. The partial engagement will sound like a click. A few other things like bad, dirty, or loose connections can cause the same symptoms. By connections I mean the cables at the battery end and at the other end, engine block for ground and starter for the positive one. A bad starter will also make a single click sound sometimes. Visual inspection of the cables along with load testing the battery and testing of the starter can be performed easily by a mechanic with the proper tools for diagnosis.