A Photoshop contest is an online game, where a Photoshop contest website will post a starting image - usually a photograph - and ask the site's users to alter the image using some kind of graphics editing software, such as Photoshop, The GIMP, or Paint Shop Pro. The contest usually asks you to edit the pictures in a humorous way, or according to a specific theme. The users then go away and edit the image to the requirements and post their results to the site. Once all the users have posted their versions of the image, they vote on the quality of the other users' submissions. The user whose image gets the most votes wins.
See also: Photoshop tennis, E-mail art, AudioEdits, b3ta.