Google AdWords is an advertising service that Google uses. It features a pay-per-click system where you only have to pay if you get a visitor, making it ideal for small or starting businesses. Since Google is by far the most popular search engine, it would definitely be wise to use its AdWords tool to help your website gain popularity.
Google AdWords basically have you bid on keywords with competitors. The highest bidders will have their website show up on the first page above all other search results. Since it is the highest search result, it will get more clicks and in turn more customers.