Depth of field
An f-stop is a camera setting that specifies the aperture of the lens on a particular photograph. The letter “f” stands for focal length of the lens.
The Exposure Triangle comprises aperture, shutter speed, and ISO. These three camera and lens controls work together to regulate the amount of light that makes it to the light-sensitive surface (aperture and shutter speed) and the sensitivity of that surface (film or digital ISO).