ANSI Animation, or ANSIMation (also capitalized as ANSiMation, ANSImation, Ansimation), is the practice of using ANSI escape codes, in conjunction with some timing mechanism (such as processing a fixed number of bytes per second), to create animated character graphics. It is essentially the animated form of ANSI Art.
A variant of it called VT100 Animation specifically targets VT100 terminals.
ANSIMation data might be stored in a file, or it might be transmitted in realtime by a server (e.g. a telnet server).