Photography & Cinematography 101 -
It's All About The Light - 1
An enormous amount of thought is put into how to light a scene.
There's the obvious parameters - how bright and where - but then there's all of these little things cinematographers do to trick you. A light that you see inside of a shot is called a "practical".
Many times practicals will have a very small wattage bulb installed and the light you see that would normally emanate from the practical is provided by a studio/set light mounted on rails above or a stand out of frame.