Question about buying a new valve cover gasket

So my valve cover gasket is leaking oil onto the engine and down into the spark plug wells so I need to get it fixed. I want to order a new valve cover online but I am a bit confused because some of them I see o-rings included in the pictures and some I don't.

1) Do I need these o-ring? What are they for?

2) If they are needed, are they just a standard O-ring that I can pick up separately?

Hopefully someone who has done the replacement before can let me know.

Thanks!

Just buy a kit, everything is included. The o rings go around the bolt heads. The gasket goes around the outside. So make sure you get a quality kit. I just went down to my local store and bought one. Not too expensive there.