In 3D design, a polygon is a 2-dimensional geometric shape that is used to construct 3-dimensional models. A polygon consists of a set of straight lines (edges) that connect a series of points (vertices) to form a closed shape. The simplest type of polygon is a triangle, which has three sides and three vertices. However, polygons can have many more sides and vertices, and are often used to create complex 3D shapes, such as buildings, vehicles and characters in video games and animations. The number of polygons used in a 3D model can have a significant impact on its visual quality and performance. A higher number of polygons can result in a more detailed and realistic-looking model, but can also require more processing power and memory to render. As a result, polygon optimisation techniques, such as reducing the number of polygons or using more efficient algorithms, are often used to balance visual quality with performance.