You know, Moe, my mom once said something that really stuck with me. She said, ‘Homer, you’re a big disappointment.’ And God bless her soul, she was really onto something.— Homer
"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.