Objects, lights and the camera are positioned using a typical 3D coordinate system. The usual coordinate system for POV-Ray has the positive y-axis pointing up, the positive x-axis pointing to the right and the positive z-axis pointing into the screen. The negative values of the axes point the other direction as shown in the images in section "Understanding POV-Ray's Coordinate System".
Locations within that coordinate system are usually specified by a three component vector. The three values correspond to the x, y and z directions respectively. For example, the vector <1,2,3> means the point that's one unit to the right, two units up and three units in front of the center of the universe at <0,0,0>.
Vectors are not always points though. They can also refer to an amount to size, move or rotate a scene element or to modify the texture pattern applied to an object.
The size, location, orientation, and deformation of items within the coordinate system is controlled by modifiers called transformations. The follow sub-sections describe the transformations and their usage.