The term that defines the amount of light passing through a lens is called aperture. It is the hole between the lens of the camera and the photographic medium wherein light passes through. This means that the wider the hole is, the more amount of light that will travel through. It is worthy to note that not all lens has the same apertures. Some of lenses have fixed ones, while others don’t.
This means that we all have to fix the lens in order to control the amount of light that passes through the lens, because lighting conditions are entirely different from each other. To make it easier to understand, apertures differ at different f-stops – f/2.0, f/2.8, f/4, f/5.6, f/8, f/11, etc.