Aperture

Aperture is the opening of the lens that allows light to reach the sensor; it is measured in F-stops. The more the lens are open, more light comes in the camera and the picture is brighter. Moreover Aperture affects the depth of field ( the distance between the closest and farthest objects in a photo). The wider is the opening, the shallower the depth of field is: Shallow depth of field. On the other hand, in the large depth of field, the background, the middle ground and the foreground are all in focus.

Shallow depth of field pictures

Large depth of field picture