This tag indicates that an image exhibits a distictive pixelized style (e.g. jagged edges, dithering). This may be either intentional or as a restriction on the software used to render it. This is common in older GIF images as well as images meant to invoke game sprites.
Pixel art is almost necessarily digital art in a rasterized format, and as such is naturally mutually exclusive with faux traditional media and vector traces.
Different from oekaki which is a very specific concept.
See also
pixelated, for this concept applied to only part of an image.
