Engine

Hello everyone;

My question what is the name of the rubber gasket that you put on when assemblying the engine?
Lets see if I can explain it better.....
I notice the top of the engine can come apart with loosning of several small bolts. There seems to be some oil like leaking out around the engine and this has been going on for awhile. My girlfriend never seemed to metion this to me until now. I know there is like some rubber that like seals the engine. Anyways.... I don't know if I am explaining this in the correct terminology. I know this part is not expense but, I don't want to go to an store and sound stupid explaining this and end up buying some part I didn't need.

Thank you for all your replys

Valve Cover Gasket.