For those beginning photography, exposure is key to capturing a great image.
Learning how exposure works will help you to take control of your camera and take better photos. Aperture, shutter speed, ISO are the elements that combine to create an exposure.
As you’ll soon learn, these elements have an effect on more than just the exposure, causing alterations in depth of field, motion blur, and digital noise.
Once you understand how each one works, you can start diving into manual mode and really take that control back from your camera.
The exposure triangle is a great way to remember that three settings control the amount of light captured from any given scene.
This will help you to understand that changing one setting will necessitate a change in the others. That is if you are photographing the same scene with the same exact lighting conditions.
Read here for all the information you need on the exposure triangle.