Search engine marketing (SEM) is the process of promoting and marketing a website through paid listings (advertisements) on search engines.
Ads on most search engines operate on a pay-per-click (PPC) model, meaning that you pay only when a user clicks your ad, and not for the ad impression (the instance in which the ad appears on the page). The other common pricing model in online advertising is cost-per-thousand impressions (CPM), in which you pay per impression, not for any clicks on your ad.
Avanti Interactive recomments site owners to advertise their site in addition to, optimizing their site for placement in the organic search results. Although it's necessary to pay for the clicks your ads receive, advertising allows you to be proactive about when and where a listing for your site appears.