The aperture setting (f/stop) you choose has a huge impact on how your photo looks by changing the amount of depth of field in your shot.  When you are shooting in Aperture Priority Mode you can select what f/stop you want to use and the camera will choose the rest of the settings while maintaining the same exposure.  In this video I go over an exercise that will demonstrate the basics of using your camera in Aperture Priority Mode to control the amount of depth of field in your shot.

Here is a series of images that illustrate the changes in the other settings that take place as you change the aperture setting.