ASCII art - NicheInterests/mistfunk GitHub Wiki

ASCII Art

1. n. ASCII text art is by far the most limited of all computer mediums. These images are created using the standard IBM extended 256-character set or Amiga-X characters. Some artists opt to limit themselves from the proprietary extended characters (aka "high ASCII"), taking advantage of only the core ASCII 128-character set (or "low ASCII"). By limiting themselves to ASCII's bare 128 characters, they gain compatibility with virtually any terminal's display without the need of any sort of emulator whatsoever. Art created using the IBM or Amiga extended character sets can only be viewed normally on their respective platforms. (source: Artpacks.acid.org)

2. n. ASCII art is any sort of pictures or diagrams drawn with the printable characters in the ASCII character set (as defined in ISO-646).

from The Artscene Dictionary

"ASCII art" at Wikipedia contains a great deal further information and, hopefully, is in no imminent danger of removal from there.