GAP is a collection of GIMP plugins that make it possible to create animations as sequences of single frames. The result can be saved as animated GIF, AVI or MPEG file (external libraries are used for this).

"The GIMP Animation Package, or GAP, is a collection of plug-ins that extend GIMP with capabilities to create and edit animations. The 2.4.0 version of the GIMP Animation Package is a bug-fix release that makes GAP usable with GIMP 2.4.x releases.A new release for the stable branch of GIMP, version 2.4.4, was released along with the GIMP Animation Package 2.4.0. You should know that this version of GIMP is a bugfix release and no new features were added..."