The goal of SEO is to gain visibility while a customer researches on the internet. To gain visibility and importance on a search engine, the website should be friendly to the search engine and cater to all its requirements.
Once the requirements are met, search engines automatically tend to rank the website higher than other websites. Improving the volume and quality of traffic to a website involves various steps and procedures. These steps and procedures differ for new sites versus established sites. Depending on the nature and trend of visitors, optimization would also require targeting various kinds of search methodologies like local search, industry specific vertical search or even an image search.
SEO process would also involve testing and validating the website codes, the site structure, issues with coding or links and compatibility check. Thus SEO will also cover the complete site testing.