This one is all about maintaining the correct exposure settings based on your desired aperture, and ultimately, depth of field
If you’re shooting portraits and looking for a shallower depth of field, you can use a larger aperture. The camera will then set a faster shutter speed to balance the large amount of light entering the lens.
Conversely, if you’re shooting a landscape scene, and want more of the frame to be in focus, you’ll use a smaller aperture. The camera will then use a slower shutter speed to compensate for the small amount of light entering the camera.