What does the keep/remove dialog in mediabay do

when checking/unchecking directories in mediabay file browser,
what do the dialog actions keep and remove actually do,
and more important, where can I read about it in the manuals.

shouldn’t keep mean those files don’t appear in search results,
but when I check the box again it doesn’t have to rescan?
cause the files are still in my searches and something doesn’t make a lot of sense here.

thanks & cheers