SEO - Search Engine Optimization, and SEM - Search Engine Marketing, on the other hand are completely different things.

SEO means to optimize your website for search engines; thus allowing a better response from visitors who search for keywords on major search engines.

SEM is marketing your website on search engines by using PPC - Pay Per Click advertising. This is a great, quick way to make a lot of sales fast, though is more costly in the long run.

We recomend doing a mixture of both, depending on the product or service, and timing of your campaign. If your search engine optimization efforts produce great results, there is less of a need to rely on search engine marketing.