Аннотация:The derivation of the term “karst” is treated. Three main approaches to the definition of the one are considered: process, phenomenon and the region, where the karst phenomenon is manifested. It is noted that karst rocks occupied nearly 30 % of continental area, during which the carbonate karst (in limestones and dolostones) prevails under evaporate karst (in gypsums, angydrites and salts). The principal karst phenomena are viewed: on the surface (karren, dolines, uvalas, poljes and karst valleys) and underground (caves). Numerous classifications of the types of karst are discussed. The recent map of karstic rocks distribution on the globe is represented.