Aperture

Aperture is a hole or an opening that allows light through. When used on a camera it can put an object in the picture in focus and everything around it out of focus, or it could put everything in the picture in focus. That depends on what your aperture is set to and the speed of your shutter. If you have a narrow aperture and a slow shutter speed, then everything in your picture will be in focus, but if you have a wide aperture and a fast shutter speed then the object in the picture will be in focus and the background will be out of focus.