Google Sync keeps your calendars and contacts synced from Google’s servers to your iPhone (or other phone) by pushing the data between the two places.
The video above explains it all but I can tell you right now that if you aren’t into the whole Google ecosystem it isn’t exactly for you. Since my Contacts and Calendars sync to my iPhone through iTunes I don’t really see any benefit to using this. I would rather live in the Apple ecosystem then the Google ecosystem just because I like the fact that everything is stored on my computer and no one elses.
even i dnt see much use of this application