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).