Aperture refers to the opening in a camera lens that controls how much light enters the camera. It is measured in f-stops, with a lower f-stop number indicating a larger opening, allowing more light to hit the sensor. This is important for capturing images in low-light conditions and affects the overall exposure of a photograph. Additionally, aperture influences the depth of field, which determines how much of the image is in focus. A wide aperture (like f/2.8) creates a blurred background, making the subject stand out, while a narrow aperture (like f/16) keeps more of the scene in focus. Understanding aperture is essential for photographers to achieve their desired artistic effects.