The following is taken from the script itself.
Arguments which are detectably either RCS masters (with names ending in ,v) or Emacs version files (with names of the form foo.~<number>~) are ignored. For each file foo, the script looks for Emacs version files related to it. These files are checked in as deltas, oldest first, so that the contents of the file itself becomes the latest revision in the master.
The first line of each file is used as its description text. The file itself is not deleted, as under VC with vc-keep-workfiles at its default of t, but all the version files are.
If an argument file is already version-controlled under RCS, any version files are added to the list of deltas and deleted, and then the workfile is checked in again as the latest version. This is probably not quite what was wanted, and is the main reason VC doesn't simply call this to do checkins.
This script is intended to be used to convert files with an old-Emacs-style version history for use with VC (the Emacs 19 version-control interface), which likes to use RCS as its back end. It was written by Paul Eggert and revised/documented for use with VC by Eric S. Raymond, Mar 19 1993.