It's a sort of backlink zero sum game theory.
The juice, ie Search Ranking Power flows into a page through incoming links, and likewise flows out of a page through outgoing links to other sites. Links from more highly ranked sites pass more link juice than a low quality link.
Using this principle one can conclude that if you are one of 100 who have placed a blog comment on a page, your backlink only has 1/100 the link juice that a single link from the page would have.
The term is believed to have been first coined by a web marketing consultant, Greg Bose.
Link juice is a term that is used by Greg Boser.It is considered by Google for ranking the sites.Simply you can say that the link juice is the method for sharing the PR
"Link juice" refers to the actual Page Rank your website's pages gain through incoming links. You don't have to have more "Link Juice" from your competitors in order to outrank them but just to have enough so that your relevant pages will stay in the primary index. It is just one important factor in SEO out of many others.
link juice is directly concerned in SEO, since this is the juice that will increases your sites rankings and bring visitors to your websites.
