Though all of the above balls are basically spheres; but then, what makes them different?

Well, each of them basically has different textures applied to them. Now, Let us understand how this is done.

We are all familiar with the world map. It is a rectangular image. We also know that the earth is not flat like this map and but it is spherical.

Note that the breadth of the top and bottom edge of the map are the same length as the equator i.e. the center, whereas in reality, these form the north and south pole, just two points on earth. Every point on the world map corresponds to a point on the earth (latitude and longitude). The same theory is used while applying textures in 3D software.

If the software knows which point of the texture is mapped on which part of the 3D object, it can create a textured object.

Since any point on the texture image can be defined by its x and y coordinates, its corresponding coordinates on the 3D surface have been conveniently called u and v coordinates and this mapping is called as UV mapping.