LOL, suuuuuuuuuuurrrrrrrrrrrrreeeeeeeee Briefly: You advertise on Googles serps and their search network with the option of advertising on the content network too. Costs are calculated by how far off they are from the analysts earnings expectations for that quarter. That's about it.
adwords is done on a cost per click basis. Unless of course you utilize their cost per impressions model. This model is based on a thousand impressions and you bid on one thousand impressions on a site in their content network. You shoudl try asking some more specific questions and you will get the answers you are looking for