A dark sky preserve is an area, usually surrounding a park or observatory, that is kept free of artificial light pollution. The purpose of a dark sky preserve is generally to promote astronomy. Because different national organizations have worked independently to create their programs, different terms have been used to describe the areas. This has led to confusion between the terms reserve, preserve, and park. The International Dark-Sky Association (IDA) chooses reserve to avoid confusion with park, when using the acronyms "IDSR" (International Dark Sky Reserve) and "IDSP" (International Dark Sky Park].