There are more than thirty types of seizures, which are categorized as either focal seizures or generalized seizures. Focal seizures, also called partial seizures, occur in just one part of the brain. They are frequently described by the area of the brain in which they originate (e.g., focal frontal lobe seizures). Two examples of focal seizures are simple focal seizures and complex focal seizures. In simple focal seizures, the person will remain conscious but experience sudden and unusual feelings or sensations, such as unexplainable feelings of joy, anger, sadness, or nausea. He or she also may hear, smell, taste, see, or feel things that are not real. In complex focal seizures, the person has a change in or loss of consciousness. People having a complex focal seizure may display strange, repetitious behaviors such as blinks, twitches, mouth movements, or even walking in a circle. These repetitious movements are called automatisms. Some people with focal seizures may experience seeing auras. These seizures usually last just a few seconds.

Generalized seizures are a result of abnormal neuronal activity on both sides of the brain. These seizures may cause loss of consciousness, falls, or massive muscle spasms. There are many kinds of generalized seizures. Two of the better-known generalized seizures are absence seizures and tonic-clonic seizures. In absence seizures, formerly called petit mal seizures, the person may appear to be staring into space and/or have jerking or twitching muscles. Tonic-clonic seizures, formerly called grand mal seizures, cause a mixture of symptoms, including stiffening of the body and repeated jerks of the arms and/or legs, as well as loss of consciousness.