You have to know three basic things that control a photo. Light - Shutter and aperture control Film or sensor sensitivity Depth of field Shutter speed is like the time you allow your tooth paste to flow out. You know how much paste you want, you have control over the speed of the flow of the paste. Same way you control the amount of light that falls on you camera sensor. Aperture is like the opening of your toothpaste case. If you have bigger opening of the tube, you slow down your paste flow or vice versa. Because amount of your tooth paste is constant. So, for a same light, you can have same amount of light with different combination of shutter speed and aperture. You increase aperture one stop, you have to decrease shutter speed one stop. Then why we have so many aperture and shutter values. Different aperture give you different depth of field. Narrower opening give a lot of field in front of the camera in focus. Higher shutter speed gives you opportunity to freeze ...
For us who walk life with photons and frames and compositions....and creativity.