In the documentation,
dist rule in the generated
Makefile.in can be used to generate a gzipped
tar file and/or other flavors of archives for distribution.
“for distribution” refers to the act of distributing.
The goal is to produce a
dist target in the generated Makefiles, so that the project maintainer can run
and get an archive appropriate for publication, i.e. a source archive with various added files so that end-users (or end-builders) don’t need to run the full Autoconf process and can just start with the usual
./configure && make.
EXTRA_DIST lists files which wouldn’t normally be included in these archives, so that they are shipped as well.
The underlying concept is that a project’s source code, for the maintainer, is the source code as expected by Autoconf/Automake/etc. But that’s not immediately useful for most people expecting to compile the project from source. So the project maintainer doesn’t distribute the “raw” source code when publishing a release, they distribute a “distribution archive” containing the generated
configure script and the various supporting tools.