“Aperture refers to the opening of a lens’s diaphragm through which light passes. It is calibrated in f/stops and is generally written as numbers such as 1.4, 2, 2.8, 4, 5.6, 8, 11 and 16. The lower f/stops give more exposure because they represent the larger apertures, while the higher f/stops give less exposure because they represent smaller apertures.”
The smaller the f-stop, the larger the aperture:
Aperture also has an effect on depth of field. The lower the f-stop, the more blurred the background will be and the more isolated the object in the foreground will become. As the f-stop increases the more the objects into the background come into focus.
I had a go at testing this myself just taking photos of a cup in the kitchen.
This is the result when using f/3.8 :
This is the result when using f/11