Hi Heather!
The monorail system has three lines that connect by going through the Transportation and Ticket Center. One services the Magic Kingdom, Disney's Contemporary Resort, Disney's Grand Floridian Resort and Spa and Disney's Polynesian Resort. The other two service direct round trips to the Magic Kingdom and Epcot. Those hotels and parks are the only ones serviced on the monorail system.
To go to any of the other parks or if you are staying at any other hotel, you will be required to utilize one of the other forms of transportation, but there are so many options and all can add to the incredible experience of your trip to Disney World in December.
For example...starting your day at the Wilderness Lodge you could take a water taxi to the Magic Kingdom, enjoy a monorail ride to Epcot, walk from there around the Boardwalk Inn, take a boat ride to Disney Hollywood Studios and then bus ride to the Animal Kingdom.
Not that you would want to do that all in one day, but the transportation choices are extensive and can be a big part of the overall experience. The entire system is designed to be able to get you where you want to go from where ever you are on the property.
For more information on the transportation system,
click here. Have a magical time!
Carrie