Stupid 

[teslamad]

How do I use this stupid img tag? Is it supposed to be html referencing an outside resource? Or does it reference an attachment? Grr… this is simple. Bigger fish to fry here. Thanks

[KOM]

AFAIK, the img and url tags require an URL.  I've been here for a couple of years and have never used either.  I simply attach any images via Attachments and other options, and the images appear inline.  Like this:

[chpalmer]

Or you can paste your attachment using the img tags.  :)

[KOM]

Turns out I misspoke when I said I never use the URL tag since I use Insert Hyperlink all the time, duh.  The attachment option might be better since it gives you a thumbnail preview.

[jimp]

One detail that could be important: Users browsing the forum that are not logged in cannot see attachments, so using inline images can be better for some cases.

You just drop the URL to an image hosted elsewhere inside the tag, like so:

[img]http://i.imgur.com/0LlOg66.png[/img]