A centroid is a point that represents the center of a geometric shape or object. In two-dimensional shapes, like triangles or polygons, the centroid is the average of all the vertices' coordinates. It is often referred to as the "center of mass" for uniform shapes, meaning it is the point where the shape would balance perfectly if made of a uniform material. In three-dimensional objects, such as cubes or spheres, the centroid is similarly calculated as the average of the coordinates of all the points in the shape. The concept of centroids is widely used in fields like geometry, physics, and engineering to analyze and design structures and systems.