Feature Request - Better Plugin Description

I have to admit that I can be a little (or even a lot) dense at times, but I am totally unclear what this plugin does, the extent to which it does whatever it does, and/or who it all applies to.

For instance, this plugin is for:

"Adding existing users to sites one-by-one"

So my questions are:

1. Adds existing users from where?
Does this plugin add existing users from any given blog on a WPMU network? Does it add users from Google's Blogger? From external WP sites? From Facebook? From my gaming site? (<-- Ok, I know the answer to this last one - snarky snark snark ; ) )

2. Adds existing users for who?
Does this plugin work only for a WPMU super admin when they are trying to add users from other sites? If so, how does that apply to a singular WP installation? Is this something any site on a given network can use? If so, what users will it pull into their database?

3. Passwords
It says on the installation page that
"Once added they'll be sent an email with their login details -- their password will be blank since they just need to use their existing password"
Existing password to what? From where? What if they are members of several different network sites individually but using the same email address? Will that throw things into a tizzy?

Please don't take this post as being hyper critical - I just don't understand what the main purpose of this plugin is - nor how it would be properly used. The who, what, why, when & where seem to be missing from this plugin's description. Hence the 'feature' request.

If nothing else, the description could really use a bit of expansion. Perhaps I'm wrong - but that hasn't happened since 1984 when I was sure that the .................. oh, never mind. ; )

~ Corey