The Aperture controls 2 things.
-First is the quantity of light coming to the camera .. a wider aperture leeds to larger quantity of light (the wide aperture is having a small number – a bit confusing I know but it will be known by time and practice. It took me a long time to get it though, maybe the below photo will show this clearer).
-Second is DOF (Depth Of Field) .. what does that mean?
Simply do you know that kind of photos when there is an object in focus and another out of focus? This what explains DOF how clear the objects in the photo are.
The wider the aperture (smaller figure) makes more focus and shallower DOF (This is with other factors and fixing another aspects in camera)
Have a look on the flower photo and compare, it will make things clearer.
Anyone needs to understand it more, please tell me.