Kinetic refers to something in motion, so this form of sculpture can be defined by its unique aspect of integrating motion into its beauty and function. In some societies, both sound sculpture and light sculpture are also considered as kinetic art, but traditionalists refer to the term only when they pertain to concrete masses in motion.
Two popularized examples of kinetic sculpture are the mobile and the fountain.
First off, the mobile is a type of kinetic sculpture that makes use of the properties of equal balance. Weight and density are taken into detailed consideration when creating works in this field. Most mobile sculptures have separate elements hanging or balancing by some point of reference. This set of elements are set in motion by a slight force of wind or air current. Alexander Calder is one of the most famous and acclaimed mobile artists of the 19th century and was best known for many of his playful depictions created by crafting metals into mobile sculptures. The mobile is also a very popular teaching exercise used to instruct art students on the aspects of balance and composition.
The fountain is a type of kinetic sculpture that associates itself with a flow of liquid. Most common fountains today are used in a grand scale as center pieces in many hotels and resorts, but there are several artists who still practice the creation of solo or small fountains, such as the japanese bonsai-garden sculptors that make use of controlled water flow in their living artworks.
The motion-creator for any kinetic sculpture can stem from many different sources of energy, such as wind and water power, electrical power, steam power, mechanical (or human) power, or even using clock work. Historians argue that the very first kinetic sculpture was made by Marcel Duchamp. A piece entitles Bicycle Wheel in the early 19th century. At around the same time (but a bit later), Naum Gabo and Antoine Pevsner created their Realist Manifesto in Moscow. Kinetic art was finally included as a novelty in the compilation.
If you would like to find Kinetic Art sculptors you could contact the Kinetic Art Organization or KAO, which is the largest international art organization of its kind.