SEO is broadly classified into two parts: On-Page SEO & Off-Page SEO
On-page SEO involves optimization through page coding. On-Page optimization may include title tags, content, meta tags, ALT tag, Anchor tag and search engine friendly design and ode that can be indexed and crawled.
Off-Page SEO is independent of page coding and focuses on obtaining backlinks from various websites to improve the ranking of the site. This method includes article submission, web 2.0, directory submission, blog posting, forum, etc.