In someone who has epilepsy, the normal activity in the brain is interrupted by bursts of activity that are more intense than usual. These bursts may cause symptoms that no one else is aware of, like a strange feeling in the body or a certain taste, smell or sight. When the activity in the brain causes any of these symptoms, the person is said to be having a seizure. Seizures are the events caused by the short disruption of the brain's normal activity. They are a sign of epilepsy.
Epilepsy is the underlying tendency of the brain to produce seizures.
This kind of seizure doesn't necessarily mean the person has epilepsy. A person has epilepsy when the brain's activity is disrupted and seizures happen over and over again. Some seizures, especially those that cause a person to lose consciousness or to fall down, can cause injuries. Although life-threatening complications from a seizure are rare, people who have repeated seizures are at risk for serious complications. So it's best for people with epilepsy to have treatment to prevent seizures from happening.