A client recently asked: Is Synchronize Outlook and CRM any different than Work Offline?
Yes, they are very different. When you select CRM > Synchronize Outlook with CRM, it synchronizes your Outlook contacts, appointments and tasks with your CRM contacts, appointment activities and task activities.
When you select File > Work Offline, it updates the local CRM database on your laptop with everything from the CRM server including customizations.
So, to summarize, the first item synchronizes your Outlook content with your local CRM database. The second item updates your local laptop database with everything on the CRM Server.