HalloweenHorrorNights is a special event that is a part of the Universal Studios experience in both Los Angeles and Orlando, Florida. This particular event is set up to be reminiscent of a haunted house and is not appropriate for children under 13 years of age.
The event goes on throughout the year, not just around the Halloween season. The Halloween Horror Nights website is a great place to visit before you arrive at the Universal Studios facilities. At the site, you can learn about what the experience is and see photos and testimonials from customers and visitors that have preceded you.
The website allows you to buy tickets and reserve spots in the individual events that take place in both Los Angeles and Orlando. It's a good idea to book these tickets in advance so that you can avoid worrying about them later on, and the tickets are discounted online.