SEO is an abbreviation used for Search Engine Optimization which means to increase your visibility on the internet and rank higher in the results of search engines based on particular keyword(s). Further, SEO is unpaid and completely depends on how you rank higher in search engine results.
Search engines use different algorithms and refine search results frequently. When you search something on a search engine, it automatically searches the web and brings the most relevant search results on the top. Keywords are certain words that indicate the user’s search. Based on the search, the results are shown. Higher the page is listed, more are the chances of the website being visited by the user. Therefore, ranking higher on the search engine results is called SEO.