During a guided tour, a lecturer from the Château de Fontainebleau will open the doors to lesser-known and/or non-accessible areas for you to visit.
In addition, if you have booked a guided tour, you have direct access to the Château during a time slot dedicated to your visit. Once your guided tour is over, you have direct access to the self-guided tour of the Château.
If you take a ticket with a guided tour there is a discount on the entrance ticket. You will find more information on this site.