Many cameras have a dial or button that controls exposure compensation. In very simple terms, a plus (+) setting makes your image brighter, while a minus (-) setting makes an image darker.
It can be used in a variety of circumstances. I'm shooting in Aperture Priority mode most of the time and let's say my subject is coming out too dark. Well, I could just open up the aperture a little more. But what if I really want to use my current aperture setting? Then I could adjust the shutter speed, but I can't in Aperture Priority mode. So I'll increase exposure compensation and it does the work for me quickly!
In the case of our little pig statue, the center shot is 0 exposure compensation. Left decreases by -1 and -2 stop respectively and right increases by a +1 and +2 stop respectively. Although the middle picture looks pretty good to me, one of the other photos may help me get either more details or light in the shadows depending on which look I want.
With many subjects you can take a shot, look at the result, and then reshoot with a different amount of exposure compensation to ensure you get the effect you want. ◕‿◕
