What is the relationship between aperture and shutter speed? how can you describe this relationship?

Both affect overall image brightness and clarity.

Aperture refers to the opening for light to expose the image, shutter speed refers to how fast it stayed open to let light expose the image.

In short, Big hole (low f-stop), more light. Faster shutter speed, less light.

but big hole also means that the object near you are more exposed than the objects far away (background becomes blurry)

faster shutter speed means objects moving can be captured clearly. (not blurry)

its always a balance between the two to achieve the desired exposure and clarity.