Depth of Field.
The aperture setting (f-stop) that you use will have an impact on the amoundt of focal range in focus, in front and behind your subject. This is known as the depth of field (DOF)
Three Objects.
I tried photographing three objects, or people, in a line about one metre appart and focusing on the object/person in the centre. I took some pictures on these settings... (F2), (F8), (F22).
Experimenting.
I experimented with using both a shallow aperture (i.e. F2) and wide aperture (i.e. F22) to show a good understanding of Depth Of Field.