Search Engine Optimization is called SEO in short.
It is a process to bring a website at top of search engine result.
There are a lot of guidelines by search engines that allow a website to go to top of search result.
There are professional SEO Expert company who optimize a website for search engine.
Even website owner himself can also do SEO work for his own website.
To optimize a website search engines guidelines should be followed strictly. Otherwise search engine can ban a website in their search result.