"Conflict" in the context of the "Publish" screen in Frontpage occurs when a
file in one location is newer (or older) than the other location
Two examples:
1) you might have a reason to need to update a file on the site, so you go
through Frontpage open the site "live" edit the page and save it. therefore
your local copy on your PC won't be updated, and you have the conflict
between the file you updated live on the server and the local copy as it was
before - simply publish the new version of that one file to the local PC.
2) You have a database (access) that you publish to the site; someone
submits data on a form, it writes the data to that database, therefore the
newer version again, is the copy on the server. You just need to publish it
down to the PC into that web.
"Unchanged" means exactly that.
"Unmatched" means FP can't find the corresponding copy on the server (if it
exists on the local machine) and vice versa.
I believe you can do a "sychronise" publish to get the files back in order
again.