What facebook App is needed?


first of all I want to start by clarifying that another company developed the site of our client in CS cart, and they asked us for the facebook app id for this setting:
I asked them what kind of app they want us to make, because as you may know when you create a facebook app you have to specify what exactly that app is doing. They referenced me to the link I mentioned above.

I am lost on what we are supposed to do, especially so since facebook share doesn’t even need an app, to my knowledge and nor there is an option for a “share” app. So, could you give us some guidance regarding the facebook app?