the number of links that point to your website from other sites.  Your external link inventory is important from an SEO point of view because the number of quality links that point back to your site have an impact of how your site page' will rank in the search engines.

The number and quality external links that you have pointing back to your site affects your site's overall Inbound Link Quality (IBL Quality) which is a key ranking factor used by search engine algorithms when ranking a webpage in their index.