Search engine optimization refers to the tweaking of on-site and off-site elements of a website, in order to appear high in the organic search results.
Unlike pay per click advertising, search engine optimization does not have a fixed cost per click (CPC). In fact, search engines receive no money in exchange for a good organic position in the search result. Consequently, search engine optimization provides no guarantee that the website will rank high in the search results or even be indexed in the search engine.
These facts make search engine optimization both an attractive and potentially risky online marketing option. The attractiveness of search engine optimization is that no investment is necessary to appear in the SERPs. Any company could get top position for its keywords by doing some optimization on the website and by getting good quality sites to link to its website. However, this is not an easy task for someone who is not experienced in SEO. The uncertainness of search engine optimization is that even the best SEO firm or individual cannot put a website on top of the SERPs with 100 percent success rate. Thus, hiring optimizers may cost a lot of money and not bring in any revenue at all.