What is SEO?
Search engine optimization (SEO) is the process of improving the volume and quality of traffic to a web site from search engines via "natural" ("organic" or "algorithmic") search results. Usually, the earlier a site is presented in the search results, or the higher it "ranks", the more searchers will visit that site. SEO can also target different kinds of search, including image search, local search, and industry-specific vertical search engines.
Is doing SEO any good for my site's rankings?
It is a good idea to do basic SEO for your sites/blog to get indexed in search engines and get traffic. Here is a list of some of the major search engines.