There are various controls to a 3D camera that simulate a real one, such as focal length and depth of field. The positioning of the camera is also limitless as the 3D artist is not restricted to where he can place a ladder.
A 3D camera can also animated, not just in location but in it's settings. For example you could animated the camera to pull away from the subject over 5 seconds and whilst doing that change the focal length to reveal more of the scene. Over that period you could also change the depth of field so as the subject may now go out of focus while the background comes into focus. Moves like that would be very complex in real life but quite simple in 3D.
If you are having 3D Renderings prepared then you will need to determine where the 3D Camera is positioned, or your viewpoint to use another term. If you are getting a 3D animation created then you will have to determine the camera path.
3D cameras can also be created from real data, which can be very evident in scenes that incorporate camera tracking.