The definition of the aperture is a measure of how much the lens is open (lens aperture) when we take photos.
When we pressed the shutter button, the hole in front of our camera sensor will open up, now was the aperture setting determines how big the hole is open. The bigger the whole open, the more the amount of light that will enter read by the sensor.
Aperture or opening is measured in f-stop. Often we read the term aperture / aperture 5.6, in a more formal language of photography can be expressed as f/5.6. As disclosed above, the primary function of the aperture is as controlling how big a whole open in front of the sensor. The smaller the f-stop number means that the bigger the hole is open (and the more the volume of incoming light), and conversely, the larger the f-stop number the smaller the hole open.
So in reality, the aperture setting of f/2.8 means the aperture is much larger than the setting f/22 for example (you’ll often find the term fully open when I hear chatter photographer). So wide aperture means that the smaller the f-number and opening his narrow means the greater number of his f.
Depth of Field
Depth of field – DOF, is a measure of how far the field of focus in the photograph. Depth of Field (DOF) which means that most of the width of the object image (the object closest to the object farthest from the camera) will look sharp and focused. While DOF is narrow (shallow) means that only part of the object at a particular point are sharp while the rest will blur / out of focus.
To obtain a wide DOF use a small aperture setting, suppose that f-22 (the smaller the aperture the more extensive range of focus) – see example photo above. Meanwhile, to get a narrow DOF, use aperture as possible, eg f/2.8 – see example photo below.
The concept of depth of field will be of much use, especially in portrait photography and macro photography, but virtually all specialties will need it.