What does it mean if you have a little bit of oil in one of the cylinders where the spark plug goes in?

With more information, I could give you a better answer, (Make, model, engine, etc) but generally, this will be caused by either worn piston rings or leaky valve stem seals. The general shade tree method to decide which is to look for a puff of smoke when you first start up in the morning. If you get the puff, but no further smoke, it is probably valve stem seals, if it smokes regularly, it is probably piston rings.

Or it could be a valve cover gasket look for oil around and on top of the intake manifold if it's there probably valve cover.

If you're talking about oil in the spark plug tubes, that's almost always the result of a bad valve cover gasket and sealing rings. Don't confuse this with head gasket--totally different animal. If you have a 4cyl engine, it's an easy DIY fix. Just make sure you buy a complete valve cover gasket set that includes the spark plug tube sealing rings.

I would have to agree with RICK on this one. Un burned oil in the spark plug tube could not make it to above the valve cover, unless a seal has failed( valve cover or spark plug tube). I would imagine if it were something more serious like a headgasket or bad piston rings, oil would burn and not make its way where brooksdavison mentioned.