Now that your web site is online, it is important - in the majority of cases - to attract the visitors that the site was intended to serve. If your site is promoted properly, it will attract internet users that are looking for the product, service or activity that your site is presenting (as stated in the first step above).
There are several ways to promote your site, some are free and others will cost you by placement or by number of inward visitors. The most cost effective way to promote your site is to have it appear 'high' in the ranking when your product or service is searched for in the major search engines. This is called Search Engine Optimisation (SEO).