What is a pixel?
A pixel is a physical point in a raster image, it is the smallest controllable element of a picture represented on the screen. Pixels are what make up the graphics on your computer, television, mp3 player, phone and other electronic devices with screens.
Image from here
Pixel art is a form of digital art, created through the use of raster graphics software, where images are edited on the pixel level. The most common interpretation of pixel art is in video games, this began in the 1970s when video games were advancing and becoming popular in arcades. Over the last few decades, video games have advanced exponentially, with these advancements comes more pixels meaning better graphics. However, in recent years there has been a large growth in Independent video games (indie) – created by individuals or small teams without video games publisher financial support – these developers create graphics which look very retro, much like they did in earlier generations, which has lead to an influx of great pixel art.
Space Invaders (1978) – image from here