DOF

DOF = Depth of Field
What does this mean?

Depth of Field determines the sharpness in front and behind the photographed subject. This is influenced by the aperture or diaphragm. The higher the F-value of the diaphragm, the higher the Depth of Field will be.

If you would like to photograph scenery where everything ( or almost everything) should be sharp, you should use a high F-value. If you would like to have only one object sharp and the rest blurry, you will use a lower F-value.

F-value: 6.7 - almost everything in the picture is clear and sharp
F-value: 4.5-only the object in the front is clear and sharp, the rest is blurry.
This effect is usually used when you want to draw attention on your subject ( e.g. portrait photography).