PageRank is a pretty complex formula that Google uses as part of how it ranks a website in the search engine results. Once upon a time, there was a pretty clear relationship between PageRank and your placement in the Google search rankings, but not so much anymore.
You can check your PageRank here:
http://www.prchecker.info
PageRank is just one of many, many signals that Google uses to rank a site, so I wouldn’t focus too much on it alone. It’s always best to focus on good, relevant content for your site.