A museum is an institution that displays and preserves objects of significance. Many museums have exhibitions of these objects in public display, and some have private collections that are used by researchers and specialists. Compared to a library, a museum hosts a much wider ranges of objects and usually focus around a specific theme such as the arts, science, natural history, local history, and other topics. Public museums that host exhibitions and interactive demonstrations are often considered to be tourist attractions, and many museums attract large numbers of visitors from outside their host country, with the most visited museums in the world regularly attracting millions of visitors annually.