Magic Kingdom Park, EPCOT Center and Disney-MGM Studios Theme Park are the three main parks within Walt's Disney World. The centerpiece of the Magic Kingdom is Cinderella's Castle, the most recognizable of Disney's logos. Within the Kingdom are a series of 'lands,' including the tautological New Tomorrowland, Fantasyland and Adventureland.
EPCOT stands for Experimental Prototype Community of Tomorrow, and its trademark silver geodesic dome is visible throughout Disney World. EPCOT Center is divided into two main sections: Future World, a combination amusement and educational park, and World Showcase, a well-presented re-creation of 11 countries - Canada, China, France, Germany, Italy, Japan, Mexico, Morocco, Norway, the UK and the USA (there's a logic in there somewhere).
Disney-MGM Studio's rides and attractions are absolutely first rate, but it's far less of a working studio than they'd have you believe. Most of the 'rides' here are 3D, with the notable exception of the Twilight Zone Tower of Terror, which is arguably the park's best and most terrifying ride. The 3D stuff in Jim Henson's Muppet Vision 3D is so real that kids (and, fess up, adults too) try to reach for the characters.
It's best to buy your tickets before you arrive, either at a Disney store or by mail from Walt Disney Guest Communications, since lines to buy tickets can be very long. There are numerous ticket prices and options. Disney World is about 20 miles (32km) southwest of downtown Orlando, west of I-4, in a town called Lake Buena Vista. The best way to access the park is by car; if that's not an option, a bus leaves every two hours from Orlando's Lynx Bus Center.