There are two main types of camshaft configurations: in the block (overhead valves) or in the cylinder head (overhead cam). This can differ from engine to engine, and each engine make might have a different number of camshafts entirely.
Wear or damage on your camshaft can negatively affect your engine performance, so you want to make sure everything is operating in peak condition. Just .001 of an inch of wear can affect your valve timing by as much as 3 degrees. More significant damage, like considerable flaking or pitting, can even damage other engine components, leading to a much more costly repair. If you notice a loss in power or fuel economy in your engine, you should take a look at the condition of your camshaft. It might be time to replace it!