A model is a person with a role either to promote, display or advertise commercial products (notably fashion clothing in fashion shows), or to serve as a visual aid for people who are creating works of art or to pose for photography. Modelling ("modeling" in American English) is considered to be different from other types of public performance, such as acting or dancing. Although the difference between modelling and performing is not always clear, appearing in a film or a play is not generally considered to be "modelling". Types of modelling include: fashion, glamour, fitness, bikini, fine art, body-part, promotional, and commercial print models. Models are featured in a variety of media formats including: books, magazines, films, newspapers, internet and television. Fashion models are sometimes featured in films (Prêt-à-Porter and Looker); reality TV shows (America's Next Top Model and The Janice Dickinson Modeling Agency); and music videos ("Freedom! '90", "Wicked Game", "Daughters" and "Blurred Lines"). Celebrities, including actors, singers, sports personalities and reality TV stars, frequently participate in modelling contests,assignments as well as contracts in addition to their regular work.