The "tags and tag cloud" switch enables a tagging system similar to what you find on slashdot and other sites. A tag is a simplistic description of the image, as one word with only alphanumeric characters (no punctuation or spaces). If your language has other characters which need to be included outside the a-z range, you can specify these in your tweaks file with the $keepchars line.

By default, anyone can add a tag either while submitting a image or while viewing it. Permissions can be changed in the usergroup permissions. There's no validation system, they appear instantly. They're displayed ordered by the frequency with which the tag has been applied to the image.

The tag cloud is a list of the most popular tags, ordered from most uses to least, shown on the front page by default. Clicking one takes you to a list of all links tagged with the word.