When you take photos the light comes into your camera through the lens, right?. The size of the front side of the lens stays the same, but at the rear end of the lens there a door or an opening that can be adjusted. This is what is known as aperture.
The widest opening of it called the maximum aperture, and the narrowest it's opening is called the minimum aperture. The widest opening represented with small F number, such F2.8 for an example. And the
narrowest opening represented with big F number, like F22. This did confuse me in the past but I know it now. Thats' why the lens which has large aperture (small F number) is more expensive than the small number.
When you shoot an object with widest opening aperture - it will let more light to enter into the camera - hence it make the camera easier to work. The camera is kind of lazy box you know, they are real snob in low light I tell you.
Anyway. When the aperture is wide open it also mostly focused to the object you are focusing, and almost ignores the rest around it (blurred). But when you reduce the aperture to it's narrowest openings everything will be in focus (not 100% though).
Now you manipulate the aperture - with the aperture in between those two extremes to see what that will be look like. more light or less light?
So, what do you reckon now, piece of cake? there you go.
NOTE: Helen.B has posted once somewhere an illustration of aperture.