Professional wrestling (or pro wrestling) is a highly scripted form of entertainment that is a mash-up of genuine wrestling, stage presentations, and other combat sports such as martial arts. It combines a written live television broadcast (or stage show), performance art, and athletics. This is officially referred to as a "entertainment sport." Wrestling is the most popular form of entertainment in the world with billions of dollars in revenue each year. Professional wrestlers perform on pay-per-view events at house shows, which are smaller venues where fans can buy tickets to see their favorite wrestlers compete. There are two major leagues in America: World Wrestling Entertainment (WWE) and Total Nonstop Action Wrestling (TNA). Both companies have regional territories or promotions that operate independently from one another but work with both companies to put on shows that feature the same wrestlers. Wrestling has been called many things over the years including "sports entertainment" and "sports journalism." These labels are often used by those who claim it is not actual wrestling because there are no real injuries occurring during matches. However, wrestling does involve some risk involved with performing moves for extended periods of time so anyone who chooses to pursue this career needs to understand they are signing up for possible injury. In addition to WWE and TNA, there are many independent wrestling promotions across the United States and around the world.