Facebook app can be used to play different games in it using online facility. In the gaming section of facebook, you can play games individually or can play with other online players from different parts of the world.
To play any game on facebook app, you need to go to the menu of facebook.
There you can see "Gaming" section. Click on it.
After clicking on it, you will see different games which will be shown to you on the game page. You can play the game according to your choice or you can search for some other game also.