An online photo-editing service. It's free but you can pay for premium.
It has a variety of photo effects, which, if used correctly, can positively enhance an image. Many of the effects Picnik has are merely dumbed-down and less-refined versions of what you can do in Photoshop, but hey, there's a reason Picnik is free.
However, Picnik is often used by young teenage girls to apply bizarre color effects and to add stupid sayings in ugly fonts to pictures, that they then add to Facebook. For this reason, Picnik has an extremely bad reputation.
Girl 1: Did you see Kathy's new profile picture of her and her sister? It looks so weird. It's really sharp and too highly contrasted, and she wrote "sIsTeRz <3" on it in some ugly text.
Girl 2: Yeah, I saw that. She must have picniked it. God, I hate that type of Picnikers.
Guy 1: Hey man, nice shot! Did you use Photoshop to adjust the color like that?
Guy 2: Thanks! Nope, I actually used Picnik.
Guy 1: Really? I didn't know you could actually make photos look good with Picnik.
Guy 2: Yeah, there's a lot you can do with Picnik if you know how to use it.