A friend of mine developed epilepsy in high school, so I know what I learned from him.
There are different kinds of epilepsy; the two I'm familiar with are petit mal (more common) and grand mal.
Petit mal seizures are sometimes not even visible to people who don't know someone is epileptic--the person seems to just zone out, or maybe their eyes go unfocused and their eyes may seem to roll. This incidence can last from a few seconds to several minutes; I've heard that it can last longer, but I've never seen it happen. However, if you happen to have a petit mal episode while you're doing something attention critical, like driving, it can be EXTREMELY life threatening to you and people in close proximity to you. That's why people with epilepsy can have such severe driving restrictions unless their doctor can show that their medication is preventing episodes over a substantial period of time. It varies from state to state what the time frame is.Â
Grand mal is what most people think of as epileptic fits--people falling down or shaking uncontrollably, biting their tongue, etc.Â
Epilepsy can be caused by a lot of factors, but the most common ones include genetics, drug abuse, and physical trauma, or more usually, a combination of these and other things.
Most of the time epilepsy can be readily controlled through medication, and very occasionally, when there's an actual physical lesion in the brain, thru surgery. That's what happened with Kevin; his seizures were much improved after his second surgery (the one to revise the lesion), and since then he's only had a handful of minor petit mal episodes, always related to his meds--a change in prescription, or missed doses, that kind of thing.Â
It can take a long time to get epilepsy under control, but once it is, most people are able to manage it very successfully for the rest of their lives.  If the seizures are grand mal type, the people around the patient will need to learn how to help protect them during the seizures--making sure their airway stays open, making sure if they flail that they don't bang their head against a hard surface, that kind of thing. It can be REALLY intimidating to kids, but if it's approached with confidence and facts, it can be handled.