All right, you scrawny beanpoles: becoming a cop is not something that happens overnight. It takes one solid weekend of training to get that badge.— Wiggum
"Pixel art" is the name given to pictures which are drawn pixel-by-pixel. They do not use any line-smoothing techniques and as such, can be reduced to very few colours (typically 16 or fewer).
This type of images are common of old console video games (such as the Game Boy) which have very few display pixels and limited colours - yet the images look so realistic.