Just to add to what Pisean has said.....
Google Adwords are the adverts which appear in Google above and to the right of the natural listings. You can set up an Adwords account to get right to the top of Google! However it is not cheap. Otherwise called pay per click, you bid on each click and pay through the nose to drive traffic to your site.
The higher the sales value of the product you are selling, and the more competition, the more you pay to have your advert at the top of the list.
It is not unknown for people to pay upwards of $20 per click, especially with things such as real estate and cars. There is no guarantee that these people will buy your product or even register on your site, so its a costly way of generating traffic!
It does work though, but be prepared to spend a lot of cash before you see a return.