Google Page Rank is an important principle that all website owners should be aware of. Created by Google's Larry Page whilst at Stanford University, Page Rank is a system that measures the importance of a web page.
Links are like votes
Page Rank assumes that all web pages are created and maintained by humans (not spammers) and that if you link to a page then you are essentially casting a vote for the content of this page, kind of like saying "this is good and worth looking at". Page Rank counts up all the links (votes) that connect to every page on the Internet and totals this up.
Now the algorithm runs again but this time the links are given different weights. If a page receives a lot of links (votes) then links from this page are given more weight than a page with few incoming links. This has the effect that receiving a single link from a highly important page grants more Page Rank than a large number of links from low importance pages.
How Page Rank influences website rankings
It would be easy to say that high Page Rank means high Google rankings but this is not the case. Page Rank is a measure of the importance of a web page but search results need to display websites that are both important and relevant. This is an important distinction as we can improve the Page Rank of a page through increasing the number of high value incoming links but if the page is not relevant to the query then it will still not display on the results page. You can't increase Page Rank by increasing the number of keywords on a page.
Of course getting a top ranking on Google is a bit more complicated than just getting a high Page Rank. According to Google themselves, there are over 200 factors that are used to rank a web page. Page Rank is just one of these factors, although an important one.
Its all relative!
Page Rank isn't an absolute measure of page importance, instead its a measure of the importance of a page relative to the importance of other pages on the Internet. This can have an interesting effect when we consider the internal links within a website.
If each page links to every other page on a website then the Page Rank allocated by these links is evenly distributed. However, if these links are not evenly distributed then some pages can receive more Page Ranks than others within the same website. This is an important effect to consider and there are a number of techniques that can be employed to change the internal structure of a website to make sure that the most important pages are given the most Page Rank.
More clicks equals less Page Rank
As site linking structure influences how Page Rank is distributed we must make sure that important content is close to the site's homepage. This is because most incoming links come to a site's homepage, this increases the amount of Page Rank allocated to this page. To benefit from this Page Rank, important pages should be linked from the homepage.
Page Rank is a measure of the importance of a page that is determined by the number and Page Rank of incoming links. Although Page Rank is important to Google ranking, it is does not score a webpage's relevance to a query so must other factors should still be considered. Site linking structure can influence Page Rank and 'flat and wide' directory structures create more Page Rank than 'deep and narrow' structures.