What is the difference between Camera Tracking and Motion Tracking ?

Motion tracking creates a motion path of an object in the 2D comp space.

Camera tracking analyses the visual parallax in a shot to create a 3D scene and camera in the After Effects 3D world space that matches the shot. This means you can place objects in AE's 3D space that will match the movement and perspective of the analysed footage. A useful technique when the camera is moving and the objects in the scene are static.

See: After Effects tutorials

Look for: "Add 3D text to video footage" in the Key Topics section