Exposure happens in three steps, starting 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 – not ideal when taking landscapes.
So there’s a bit of give and take and I go into full detail about that in this post.
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.