The aperture is also referred to as the f/stop. A stop is a measurement of light. Shutter speeds, ISO, and aperture can all be talked about in “stops.” However, that is just a bit too technical for what we will be learning in Photography 101, so for now, you only need to remember that aperture and f/stop are the same thing.
The aperture is the opening of the camera lens that allows light to enter the camera. This opening can be changed to allow more or less light into the camera.
Standard aperture openings are f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, and f/32. Your lens may have extra apertures, such as f/1.2 or f/1.4. Additionally, digital camera readouts may also show measurements of numbers that fall in between these standard measurements. For example, f/6.3 is on my camera, and it measures a partial “stop” of light.
Apertures can be a little confusing. The main thing to remember is that the lower the f/stop number, the bigger the opening and the more light that will be let into the camera. F/2 is the largest opening for the lens example discussed above, while f/32 is the smallest opening.
Each of these standard measurements also interrelate. Each f/stop lets in twice as much light as the next higher number but half as much light as the next lower number. For example, f/2.8 lets in twice as much light as f/4 but half as much light as f/2. —CWN