Sport is any competitive physical activity that aims to maintain or improve physical ability. There are hundreds of sports that can be individual or team activities. Individual sports involve a single participant competing, such as running or swimming. Team sports require players to work together towards a common goal like winning, as seen in basketball, rugby or volleyball. The Olympic Games originated in ancient Greece and feature the world's most popular sports, including summer sports like athletics, gymnastics and swimming as well as winter sports like alpine skiing, bobsleigh and ice hockey. Some unusual sports featured are hurling, curling, skeleton and lacrosse.