Camera overrides
Knowing what the active camera does and how to change it is not the whole story. What if we want to view or render the scene with something other than the active camera? There are reasons for and methods of doing so.
Viewing with a local camera
When we play the animation in Camera View, the played-back animation faithfully switches cameras where it ought to, so we get an idea of how the rendered animation will look in realtime. Depending on the circumstances though, this camera switching might not be what we want to see all the time. Say we’ve got a camera that is not active, but we want to review a part of the animation through that camera anyway. Or maybe we need to look through that camera in order to figure out exactly when we ought to switch to it.
In such cases, you can always make a camera the local camera. To set up a camera as such for a given viewport, open up the right-hand sidebar (N) of the 3D Viewport and go to View | View | Local Camera...