Backlinks are links that are coming into your website. In the world of SEO Content is King and Links Building is Queen. To measure how many links you currently have simply go to http://siteexplorer.search.yahoo.com/ Yahoo provides the most comprehensive list of incoming (backlinks) to your site. Simply put the url of your site into the input box next to the explore url command button. Second, click on the inlinks tab. Third, change the option "from all pages" to "except from this domain". Fourth, change "only this url" to "entire site". That will display how many inlinks (backlinks) you have. The quality of those links will be determined by how well the content from that linking page (including the anchor text (and if the anchor text is a keyword)) matches with the content on the landing page (page the link refers the visitor to (not always the home page and if not the home page then it is known as a "deep link"). To begin your own link building strategy you should research your competitors' link building efforts. Try to get links on the sites they use for links to your site. There is also a plethora of social bookmarking sites that allow you to post articles, press releases, etc. that include links. You should include 2-4 links (using keyword-rich anchor text)within a paragraph (4-5 sentences). Some of the social bookmarking sites have a strict "nofollow" link policy so the search engines won't recognize them, but the potential traffic from those sites shouldn't be ignored. There are also a few link submission sites out there....but I'll leave the research for those sites up to you.