Perspective Matching is the process of determining the position of a camera when it took a photograph so that 3D graphics can be combined with that photograph. To combine 3D graphics with a photograph you have to tell the 3D rendering program where to place the camera, how to orient the camera, and the specification for the camera’s internals so during rendering the ‘perspective matches’.
See Perspective Matching and Using Camera Station Information, Control Imports and Idealize Project.