Aperture size – The aperture of a camera is the opening through which light travels before it reaches the camera sensor. The smaller the number is, the bigger this opening is, allowing for more light to pass.
Focal length (35mm equivalent) – The lower (shorter) the focal length number, the wider the shot will be. Conversely, longer focal length cameras produce narrower frames, which can be used for telephoto (zoomed-in) purposes.
Camera sensor size – A bigger camera sensor is able to capture more light, and thus produce better photos.
Pixel size – The size of an individual pixel on a camera’s sensor. The bigger, the better.