There are two type of SEO
1. On Page SEO
2. Off page SEO
On page SEO worked of meta tag, title tag etc. It is specially seen on page factor of your index page, set your keyword rankings. and off page words in the web page URL, title tags, meta tags, headlines, sub headlines, keyword density, words start page, page content, words that are bold in touch , words, site navigation, website link structure and a number of other reasons.