For clueless people like I was, here are the basics. There are four parks. If you are traveling with youngish kids, don’t try to do more than one park in a day. Won’t do the parks justice, it’s exhausting, and it takes longer than you would think to travel between parks. Also, I thought the Harry Potter world was Disney. It’s not. See my entry on my experiences at Universal Orlando.
Magic Kingdom
This is what you think of when you think of Disney. Cinderella Castle, Dumbo, Teacup ride, It’s a Small World, etc. You can meet princesses, pirates, characters like Minnie and Donald, and fairies like Tinkerbell. The rides are mostly tame – but some kids will be scared by ones like the Haunted Mansion and Pirates of the Caribbean; and rides like Space Mountain have height restrictions.
Epcot

Epcot is connected to the Magic Kingdom by monorail. You can get a small taste of different countries’ architecture and food. Rides include the popular Soarin’ hang gliding ride and Test Track, where you can customize a car and “drive” it. You can meet characters here like Aurora and Alice in Wonderland. In my experience, Epcot is not so interesting for young kids.
Animal Kingdom

Need to get to the Transportation Center then take a bus. It took us about an hour to get there from the Bay Lake Towers at the Contemporary. The safari ride is excellent – a good variety of animals that you see relatively close up. It’s hit or miss getting wet on the Kali River Rapids ride but if you get wet you are miserable until you dry off. We found out about the lockers and rain ponchos too late. Rides like Expedition Everest and Dinosaur are good for older kids. If you are nature oriented, this is a great park for you. We enjoyed everything but the wait at the Rainforest Café here.
Disney Hollywood Studios

This is also a big hike from the Magic Kingdom area. In my experience the best part of this park is Toy Story Midway Mania. I have two girls and none of us had seen the Toy Story movies and we don’t like to shoot things so I was skeptical, but it is the most popular ride for a reason. It is well orchestrated, fun, interactive, colorful, and competitive. If you have Star Wars fans, kids can do Jedi training. There’s a Frozen Sing Along (no meet and greet with Anna and Elsa– that’s at Magic Kingdom) and a stunt show. Older kids/adults might enjoy the Tower of Terror or the Rock ’n ‘ Roller Coaster. From May 4 to June 14, 2015 you can book a meal with Minnie, Mickey, et al dressed as Star Wars characters: https://disneyworld.disney.go.com/dining/hollywood-studios/jedi-mickeys-star-wars-dinner-hollywood-vine/