Back links (inbound links) are the links that are directed to your site from other sites. The number of incoming links is an indicator of your site's popularity. You can consider each incoming link as a vote for your site. The more votes that you have from reputable sites the higher your page ranking.
Check Your Back Links
You can check the links back to your site:
Yahoo - type in the search box
linkdomain:http://the domain name
From Yahoo you will also get the links for your own site you need to select "exempt from this domain" it is in the show inlinks in the drop-down menu at the top of the page
Google - type in the search box
link:http://the domain name
