Hotlink

To hotlink an image is to load it in an &lt;img&gt; tag from a source that didn't give you express permission to do so.

E.g.: If I were to post &lt;img src="http://www.someguy.com/funnypic.jpg"&gt; into a thread, without permission of someguy.com's owner, that's hotlinking. Every time someone loads the image, it costs someguy.com bandwidth. They're paying for your lulz. It's generally frowned upon.

To avoid hotlinking, either have your own server space you can use for hosting images, or host them on a site specifically created for that purpose. The downside to having your own server space is that you'll be the one paying for bandwidth. The downside to a third-party host is that you have to play by their rules, which usually means no nudity.

Links
Free image hosts include:
 * TinyPic
 * ImageShack
 * Photobucket