1. APERTURE

2. Aperture description…
referred to as the opening inside a photographic lens.
The size of the opening in a camera lens regulates the amount of light that passes through onto the film (or sensor) inside the camera the moment when the shutter curtain in camera opens during an exposure process.
Regulates the depth of field within a photo.
Aperture size is usually calibrated in f-numbers or f-stops. Each of this value represents one time the amount of light either more or less in quantity.

5. CONTROLLING THE AMOUNT OF LIGHT:
The smaller numbers on the left side (starting with f/2.8) let in MORE light
The largest number on the right (f/22) lets in the LEAST amount of light
                                                                                           

6. Depth of Field
Refers to the amount of the picture plane that appears to be in focus
May be referred to as shallow, medium, or wide depth of field

7. CONTROLLING THE FOCUS- DEPTH OF FIELD:
The MORE light let in, the the SHALLOWER the depth of field (fewer parts of the image are in focus)
The LESS light let in, the WIDER the depth of field (more parts of the image are in focus)
                                                                               

8. This effect may be very dramatic with portraits.
                              
At f/2.8 only the focused subject will be sharp; foreground and background won't.
This effect may be very dramatic with portraits.

9.                               
Many photographers prefer very sharp images. With a really wide aperture images may look soft. Using a smaller aperture will improve the sharpness of the photograph dramatically.

10. With smaller apertures (f11) everything in the scene will be very sharp. Many lenses have a so-called sweet spot where the lens reaches the maximum sharpness (in many cases at f/8 or f/11).