rsync (and thus grsync) aren't a "sync" in the way you might think of it from a Palm based system (that is; syncing a calendar or a contacts list) -- those tend to have a "merge" concept, since they work on the "record" (calendar entry or contact) level.

Rather rsync works on a file level, and similar to the Palm in some ways (think "Palm overwrites computer" and "computer overwrites palm") -- there is a concept of a primary file that will win in a tie. Effectively; rsync works such that a set of files are copied remotely. From there, there is additional flags to indicate "remove a remote file if a local version doesn't exist", and "newer overwrites older".

You can specify that the remote copy is the primary, or that the local copy is - and then things are made to match up according to your preferences.

You should really check a "man rsync" in google for a reference page to go through a lot of the available knobs that can be turned ... (and make a copy of your files before experimenting ....).