Aperture is the hole or opening of a camera lens that lets a certain amount of light in depending on the size of said hole. With bigger lens sizes there will be a shallow depth of field and smaller lens sizes there will be a larger depth of field. Depth of field is the amount we can see that is in focus. For example with shallow depth of field we can only see a smaller amount of field than a wider lens which if focused would show everything around it in focus. The higher the aperture the wider the D.O.F.