The term 'Shapes of Parentheses' refers to the two main types of parentheses used in writing: round parentheses (also known as curved parentheses or simply 'arcs') and square parentheses. Round parentheses are the most commonly used type of parentheses, and they are used to indicate a parenthetical phrase or an aside. Square parentheses are used less often, and they are typically used to indicate a clarification or an afterthought.