There are more than 300,000 search engines in addition to numerous intrasite search engines. The giant in the industry is Google. Google claims to have about 55% of the traffic while all other search engines wresting the remaining 45%. It makes lot of economic sense to advertise on Google search engine rather than considering your ads on others.
Google runs two ad programs called AdSense and AdWord. AdSense makes sense to webmasters to increase their revenue (share it with Google). AdWord is of use to businesses that want to advertise their products on the web. You pay on Google on a per-click basis. In other words, you pay only when someone clicks on your ad on the Google page. You can control your budget by asking Google to cap the ad spend to X amount. The moment your ad budget exhausts, Google removes your ad form the place. These ads are based on keywords, and you can decide to place your ad for a particular keyword. When users start the searches based on the keyword, your ad appears in the sponsored listing on the right side of the page. If the user clicks on your ad, you pay, otherwise you don’t. Google ads are text type only.