Search engine optimization (SEO) is a set of rules that can be followed by website (or blog) owners to optimize their websites for search engines and thus improve their search engine rankings.

It is a great way to increase the quality of their web sites by making them user- friendly, faster and easier to navigate.

Two categories of SEO
Off page SEO
Off page SEO refers to techniques that can be used to improve the position of a web site in the search engine results page (SERPs). Many people associate off-page SEO with link building but it is not only that, off Page SEO has to do with promotion methods – beyond website design –for the purpose of ranking a website higher in the search results. Read more ==http://www.olarsblog.com/2017/06/off-page-optimization-seo-vs-on-page.html

Howdy! On-page optimization and off-page optimization are two critical aspects of search engine optimization. While both are essential for achieving higher search engine rankings, they focus on different areas of the website.
On-page optimization involves optimizing your website's content and structure to make it more search engine friendly.
Off-page optimization, on the other hand, refers to the activities you do outside of your website to improve its visibility and ranking.
However, first you should use the tech site audit in order to learn about what flaws regarding On-Page and Off-Page optimization your site has.
I hope my answer will help you!