It's simple, Pixel art is a form of digital art created through the use of software,where images are edited or made on the pixel level. This aesthetic for this kind of graphic comes from 8-bit and 16-bit devices or video game consoles from the 1960's (maybe). This type is art is one of many favored by many people, including myself. Also there is a crap ton of pixel creating software, but I mostly use a software called Piskel. It's not that hard to master too, all you need is a pixel creating software and a wide imagination and you will be creating some fine art.