What's "direct linking"?

Answer 1

direct linking is providing content on your site that IS NOT on your site. As an example, direct linking an image would be to use the direct location of an image not on your site.

Direct linking is a bad practice because a site operator is now paying (directly or indirectly) for providing YOU content. If you had a site that had a 1gb transfer limit and a high traffic site was direct linking your images, as soon as you exceeded your 1GB limit, you start getting charged.......sometimes this charge can get pretty huge.