Exposure happens in three steps. We will start with the aperture. This is the hole inside the lens, through which the light passes.
It’s similar to the pupil of your eye. The wider the aperture, the more light is allowed in and vice versa. Simple? Not quite.
As the aperture widens, the f/number gets lower and more light is allowed into the camera. This is great for low light. But be aware that it’s going to make the depth of field very shallow. This is not ideal when taking landscapes photos.
So this is a short summary, The aperture is the preferred setting to set first, as it directly influences how much of your scene is in focus. But, if you are looking to create motion blur, then it is second to the shutter speed.
Exposure will be much easier if you can memorize the f/stop scale.
The scale is as follows: f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22.