Final answer:
Cubism, initiated by Pablo Picasso and Georges Braque, is a 20th-century art movement that presents subjects in abstract geometric forms and multiple viewpoints to challenge traditional perspectives.
Step-by-step explanation:
Cubism, spearheaded by Pablo Picasso and Georges Braque, was a transformative art movement of the early 20th century. Rejecting the traditional perspective and inspired by African and Native American art's simplicity, Cubism involves breaking down subjects into geometric forms and reassembling them in an abstract way to represent multiple viewpoints simultaneously. This method emphasizes the flat two-dimensional plane while giving an illusion of three-dimensionality, altering how space and form are perceived in art.