Reading the make's manual page:
`shar' Create a shell archive (shar file) of the source files.
What is a shar?
It's a shell archive, a self extracting executable shell script which is meant to be a convenient way to ship archives of files and have them appear simply by running the script.
An example is shown in the transcript below which gives only one file from the archive, output.txt
:
pax> cat shar.bash
#!/bin/bash
tr '[A-Za-z]' '[N-ZA-Mn-za-m]' >output.txt <<EOF
Uryyb sebz Cnk.
EOF
pax> ./shar.bash
pax> cat output.txt
Hello from Pax.
That's a fairly simplistic one since it only delivers one file, and it doesn't compress it at all, but it should give you the general idea.
A real one would probably give you something like a set of files combined with tar, gzip and uuencode, which would then be passed through uudecode, gunzip and tar to deliver the original content.