Disc dog is basically playing fetch with a frisbee with a dog. People throw the frisbee and the dog tries to catch it mid-air and bring it back to the person. It's like a game for the dog and the person, and they have a lot of fun doing it together. Some people even compete with their dogs to see who can do it the best. It's a great way for the dog to get exercise and for both the dog and person to bond and have fun.