There are two basic methods still in use today that would allow a webmaster to submit their site to a search engine. They can either submit just one web page at a time, or they can submit their entire site at one time with a sitemap. However, all that a webmaster really needs to do is to submit just the home page of a web site. With just the home page, most search engines are able to crawl a site, provided that it is well designed. Most websites want to be listed in popular search engines, because that's how most people start their search for a product or service. A searcher, (or AKA "User"), seek information on the web, using a search engine. Websites that appear on the first page of a search are, usually, called the top 10. Clicking on the blue URL / hyperlink causes the web page / website to appear in the web browser.
Thus, webmasters often highly desire that their sites appear in the top 10 in a search engine search. This is because searchers are not very likely to look over more than one page of search results, known as a SERPs. In order to obtain good placement on search results in the various engines, webmasters must optimize their web pages. The process is called search engine optimization. Many variables come into play, such as the placement and density of desirable keywords, the hierarchy structure of web pages employed in a web site (i.e., How many clicks from the home page are required to access a particular web page?) , and the number of web pages that link to a given web page. The Google search engine also uses a concept called page rank. PageRank relies on the uniquely democratic nature of the web by using its vast link structure as an indicator of an individual page's value. In essence, Google interprets a link from page A to page B as a vote, by page A, for page B. But, Google looks at considerably more than the sheer volume of votes, or links a page receives; for example, it also analyzes the page that casts the vote. Votes cast by pages that are themselves "important" weigh more heavily and help to make other pages "important." Using these and other factors, Google provides its views on pages' relative importance. - Read More at Wikipedia