Well the dice rolls is, you can create different dice to use and you pick the number of faces and change the pictures according to the results you want.
For example, to make a six sided die, you'd make a 6 face'd die and add a picture of each side of a die (1, 2, 3, 4, 5, 6) to the sides.
then someone can roll that die in a post and whatever account is set up for it will post the results. It's basically just a way of creating games of chance or probability to succeed in an action, in the case of making an RPG game out of it.