Captions are the little bits of text that accompany an image. They can be witty, funny, fucktarded, unfunny or downright tl;dr. demotivators' and other memes are typically fueled by captions. Without the captions all you would have is a lame image that was slapped together in five seconds in GIMP worth significantly less lulz.
Captions can also be added to text on a webpage. For example, many words in any given article on Encyclopædia Dramatica will show as hyperlinks. Mousing over these words will present a caption text in many browsers, indicating the subject matter of the page that the link points to. Asture users of the ED site will be able to increase the lulz content of the current article by substituting the caption text for the actual text in the article being read at the time.
An example is as follows:
|Captions is part of a series on Language & Communication|
Captions is part of a series on