Style. An art movement is a tendency or style in art with a specific common philosophy or goal, followed by a group of artists during a restricted period of time, or, at least, with the heyday of the movement defined within a number of years.
Art movements were especially important in modern art, when each consecutive movement was considered as a new avant-garde. According to theories associated with modernism and the concept of postmodernism, art movements are especially important during the period of time corresponding to modern art.
The period of time called modern art is posited to have changed approximately halfway through the 20th century and art made afterward is generally called contemporary art. Postmodernism in visual art begins and functions as a parallel to late modernism and refers to that period after the modern period called contemporary art.
The postmodern period began during late modernism, and according to some theorists postmodernism ended in the 21st century. During the period of time corresponding to modern art each consecutive movement was often considered a new avant-garde.
Also during the period of time referred to as modern art each movement was seen corresponding to a somewhat grandiose rethinking of all that came before it, concerning the visual arts. Generally there was a commonality of visual style linking the works and artists included in an art movement.