The term “link juice” is a commonly-used term within the SEO community which refers to the amount of authority that a website or web page has based on the quality and quantity of links that it has obtained from other web pages.
For a website to rank higher on major search engines such as Google, Bing, and Yahoo!, it must have obtained links from other websites. The amount of “link juice” that a website or web page has is dependent on how many links it has, as well as how much authority (or “link juice”) that those links have.
Other factors that are included in determining the amount of worth that a link carries include how relevant the content and other outbound links that the particular web page has, the domain age of the linking page, the IP address and C-Block of the web page, etc.
For more information on link juice/authority, feel free to visit the following resources:
Open Site Explorer by SEOMoz- Find out how much authority a website or individual web page has for free (up to 5 searches per day for free/non-registered users)
What is Mozrank by SEOMoz
MajesticSEO– A Paid tool that allows you to see a more comprehensive report when it comes to analyzing a website’s inbound link structure.
What is Google Pagerank by Wikipedia