Pet rabbits kept indoors are referred to as house rabbits. House rabbits typically have an indoor pen or cage and a rabbit-safe place to run and exercise, such as an exercise pen, living room or family room. Rabbits can be trained to use a litter box and some can learn to come when called. Domestic rabbits that do not live indoors can also often serve as companions for their owners, typically living in an easily accessible hutch outside the home. Some pet rabbits live in outside hutches during the day for the benefit of fresh air and natural daylight and are brought inside at night.