When someone searching the Web and type in a key word or few words about what they are looking for, results are listed with few suggestions highlighted at the top of the search results and/or to the side of the top of the page. This is because those advertisers paid a fee to the search engine to put them on the top. When someone clicks on them, then the search engine get paid by the advertiser. For you to get on this kind of priority, you have to bid with the others who are vying for the same spot and win your place. However, you will be charged only when someone click on your advertisement.
Since most search engines are providing geo-targeting specific to certain area, now small businesses can benefit from this form of advertising. You can set up an account to review the effectiveness of this form of advertising.
This form of advertising can supplement not replace your traditional form of advertising through your own Web site.