Google Sync now features push Gmail, as well as the already present Google Contacts and Google Calendar support. Until now Google Sync has provided useful but somewhat limited functionality for iPhone, Symbian S60 and Windows Mobile users, but with Gmail now supported there are obvious benefits of having an ‘always-on connection’. 
The Sync service was released in beta form in February and has to date supported just Calendar and Contact details. The Gmail sync option integrates into your handset’s native email client, and will push-update automatically, meaning that ‘your inbox is up to date, no matter where you are or what you’re doing’, so says the official Google Mobile Blog. The full package also offers the option of syncing all, or any, combination of the supported services. To check out Google Sync for yourself visit m.google.com from your mobile, or desktop, browser. Google Sync, learn how to enable Gmail sync.
Here is The Video How Google Sync Works:
