SEO is a process of getting more and more visitors to your website by making it rank higher on the SERP (Search Engine Results Page). Although it’s the search engines that rank your site (google, bing or yahoo), but good SEO initiatives help to ensure that your site is accessible to those search engine and improves the chances that the site will be found by the search engine.
Obtain a high placement (or ranking) on a search engine results page naturally without the influence of paid advertising
A practice of optimizing content and codes on individual web pages in order to rank higher and earn more relevant traffic on search engines.
Acquiring hyperlinks from other websites to your own can act as a signal to search engines that your site has content which is worthy enough to feature on top of SERP