PageRank is one of the factors that Google uses to evaluate your web site and determine its position in the Google search engine results. PageRank is a number from 0 to 10.
Generally, if your web site has a higher PageRank, it will appear earlier in Google search results pages, all other factors being equal. In fact, you can see a significant improvement in where your pages appear in search engine results when your PageRank increases.
How do you find your PageRank? Install the Google Toolbar. You can get it for free at this link:
http://toolbar.google.com
After you install the toolbar, you will see the PageRank in the middle of the toolbar. It may have a small green bar. Hold your mouse over the green bar to see the Google PageRank for the site you are viewing.
So how does Google determine your PageRank?
Google interprets a link from page A to page B as a vote, by page A, for page B. Google looks at more than the sheer volume of votes a page receives, however. Google also looks at the page that casts the vote. Votes cast by pages that are themselves important weigh more heavily and help to make other pages important.
How can you improve your PageRank?
By getting votes from important pages (or, links to your web page from other web site pages that themselves have a high PageRank).
You can also be sure to include plenty of relevant, useful, fresh text in your pages. This is useful for Google, since you are providing information for the search engine to index, and it is useful for the people who visit your web site too.