What is an advert code for search engines?

[Solyom]

Hi there!

I parked a few domains successfully, but there isn´t any traffic yet.
I just read something about an advert-code you get or should have with search engines like Google , Yahoo, etc.
What is this and how can I get this? How costly will that be?
I there another way to get traffic onto your sites?

Thanks for every helpful reply,

Solyom