FileMaker Go runs on the iPhone and iPad. In many respects it is very similar to FileMaker Pro in the way it connects. There is a difference is capabilities however. You cannot design your database using Go but there are several things you can do with Go you cannot do with FileMaker Pro (Desktop).
Unlike FileMaker Pro - FileMaker Go for both the iPad and iPhone are free on the App store. Instead of charging for the software direct Claris make a connection charge for each copy of Go that connects to a FileMaker server.