Links are considered either "external" or "internal" depending on perspective. Generally, a link to a page outside the same domain is considered external, whereas one in the same domain is considered internal.
However, these definitions become clouded when the same organization operates multiple domains functioning as a single web experience, e.g. when a secure
commerce steroids website is used for purchasing things displayed on a non-secure website.
Similarly, a blogging website might have thousands of different blogs, in which context one might view a link as "internal" only if it linked within the same blog, not to other blogs within the same domain...