Map Of Zync
Here is a little map of how it all fits together...
Click the image for a larger version.
Note that this diagram shows FileMaker Server or FileMaker Pro as your host: GoZync can work without server, providing the mobile files can see your shared FileMaker Pro databases.
And you do not need FileMaker Server Advanced if you use server, just regular FileMaker Server or regular FileMaker Pro is all you need to host a GoZync enabled database.