Larger apertures or smaller f/stops such as f/1.4 are used to have blur or depth of field. Smaller apertures or larger f/stops such as f/8 are used to have everything in the image to be sharp. So if you are taking a picture of say a mountain and the surroundings, you would want to have a smaller aperture to keep everything sharp. But if you were taking a picture of say a tree with something in the background, you would want to have a larger aperture.