SEO is making your sites SE friendly, attracting visitors, promoting your site in such a way as to make your site popular and easily searchable by users for the targeted keywords. In short, it is converting your visitors to your customers/clients.
Search Engine Optimization (SEO) is often careful the additional technical part of Web sites marketing. This is correct bcoz SEO does assist in the promotion of web sites in addition to at the similar time it needs some technical information like basic HTML.
SEO is a magic which show results only if techniques are applied in rules and by obeying google and yahoo. This magic only seo magicians know.