What are seizures? A seizure is a temporary abnormal firing of the cells in the brain. There are two type of seizures: focal seizures, or seizures that occur in part of the brain, and generalized seizures, or seizures that affect the entire brain. A single seizure does not usually require treatment because it is not uncommon for a person to experience one seizure and never have another one. Having one seizure does NOT mean that a person has epilepsy.