A seizure is a brief electrical disturbance in the brain. There are different kinds of seizures, and each person's seizures are unique to them. If a person has a single seizure, they do not have epilepsy. Just as there are different kinds of seizures, there are different kinds of epilepsy.
Epilepsy is a syndrome.
A syndrome is a collection of symptoms and physical signs that occurs due to a specific disease. Symptoms are problems that a person experiences due to an illness. Fever and pain are two examples of symptoms. Physical signs are abnormalities which can be seen on a physical examination. Redness and swelling are two examples of physical signs.