SEO or Search Engine Optimization is the act of enhancing the quality and volume of site visitors to a specific site or even a blog from search engines. The purpose of SEO is not to bring customers to your website but to get them to click on the advertisements, sign up for the mailing list etc. SEO targets free traffic rather than paid or direct traffic. It is generally agreed that every visitor to your website or blog should be targeted and this can be done by search engine optimization. For example if you are selling a product on eBay then you need to target potential buyers rather than just collecting email addresses.