Google AdWords is a form of pay per click (PPC) advertising. It allows you to create an ad, choose the keywords to match your ads, set a maximum amount you are willing to pay per click and then pay only when someone clicks on your ads. You can also set daily and/or monthly budgets, so you have complete control of the cost of your campaigns.
The real value of AdWords ads is that they are shown to the type of person who’s already interested in your product or service. The ads appear just moments after the user typed in a search term for that very product/service! Compare this to the unwelcome cold call in the middle of dinner and the difference is clear!