Aperture is the adjustable lens opening that controls the amount of light allowed into the camera. the smaller the aperture the greater the depth of field. Whereas, a wide aperture gives you a shallow depth of field which leads to only the foreground is sharp. A narrow aperture gives you a deep depth of field which means everything is sharp.
depth of field
depth of field is the distance between the nearest and further objects in a scene that appear to be sharp/ clear in the image.