leaking valve cover

i recently painted my valve cover and now that i pt it back on it leaks a little bit of oil. do i just need a new rubber seal? also, as a side note, what exactly is a gasket and what does ti do? i know its unrelated but i think that rubber piece between the block and the valve cover is a gasket.

Yep, that is your gasket. You may need a new one. Make sure you clean the surface of the valve cover and the head well. A little silicone sealant can help also. The gasket makes up any imperfections in the mounting surfaces to make sealing easier.
Good Luck.

Yeah use black RTV sealant, lay down a bead on the valve cover, smooth it out with your finger, apply gasket, another small bead then apply valve cover to block
I just painted and put my valve cover back on last night, no leaks, but I also dont have a gasket on mine...not needed on my model, just plenty of black RTV sealant

BTW, the black is high temp and more resistant to oil, some people recommend the blue, but not me

Post a pic of your Valve Covers, what color are they now?