You can use the major search engines such as Google, Bing and Yahoo, where the web pages and other content such as videos or local listings are shown and ranked based on what the search engine considers as the most relevant to users.
SEO is the art of improving and promoting a website to increase the number of visitors coming to the website from respective search engines. There are many aspects of SEO, from the words on your page to the way other sites are linked to your one.