Aperture is a critical setting for photographers because it determines how much light enters the camera and hits the image sensor. A wider aperture lets in more light, while a narrower aperture blocks out some of the light. By controlling how much light enters the camera, photographers can control how their final images will look.
For example, if a photographer wants to capture a photo with a shallow depth of field (where only the subject is in focus, and the background is blurred), they would use a wide aperture setting. On the other hand, if they wanted to photograph a landscape with everything in sharp focus, they would use a narrow aperture setting.
In general, wider apertures are better for low-light photography and action shots (since there is less risk of blur), while narrower apertures are better for landscape photography and still life shots (since everything can be kept nice and sharp). Ultimately though, it all comes down to personal preference and what kind of look you're going for in your photos.