Definition: Google juice is a slang term for PageRank. One of the ways Google determines the relevancy of things you search for is by looking at all the backlinks, or the pages that link to it. It's like a popularity system based on hyperlink "votes."
Not all backlinks are created equal, however. Pages with higher PageRank (more Google juice) transfer more relevancy to pages they link to. So rather than focus on sheer quantity of links, you should focus on the quality links and try to attract or create links from pages with the most Google juice.
