Epilepsy refers to repeated seizures over a period of time. Anything that damages the brain in the right area can cause epilepsy. Idiopathic means we cannot find the underlying cause of the seizures. Idiopathic epilepsy is, in a number of breeds, believed to have a genetic link.
For more information, the American Kennel Club (AKC) Canine Health Foundation has a great article on Understanding Canine Epilepsy.
If your dog is having seizures:
Please talk to your vet, and because idiopathic epilepsy is believed to have a genetic link, be very sure to keep your breeder in the loop as well.