Whenever someone searches on Google, the results are displayed on a Search Engine Results Page, or SERP. The web pages listed on the very top of the page, the ones in a different color, are paid or sponsored links, but under those, the web sites and pages Google feels give the best answer to the search are listed.
Through the use of page rankings, Google attempts to provide its users with the best, the most relevant, and the most consistently referenced pages about the search query. The higher the page ranking, the higher on the SERP the website is placed, and higher rankings result in increased traffic.
Although they aren’t displayed, the pages are ranked numerically. To achieve the numbers, Google determines how important the page is through a number of factors, not all of them publicly known. One criteria used, however, is the number of other pages that link to it.
If each page that links in is thought of as casting a vote, Google adds up the number of votes to determine the page ranking. When it tallies the votes, however, not all votes are equal. A page that Google considers more important will weigh more than one Google feels is less reliable, much like the way a national film critic’s opinion may be worth more than one whose column is only in a small, local newspaper. If trusted and highly regarded websites have links to your pages, your Google page ranking will be enormous.
There are other factors that affect a page’s pagerank, but the value based on incoming links is one of the higher. Google, and others, consider it to be a worthwhile and valid test because simply having many incoming links isn’t as highly valued as having “good” ones. This page ranking reduces the prevalence of server farms, where numerous websites are created simply to link to each other and increase each other’s page rankings.
Outgoing links are also considered, and links from your site to ones that Google doesn’t think very highly of can actually reduce your page’s ranking. Internal links, those from within your own site, can be counted and included in the “vote” totals, and the more pages your site has, the better the results can be.