Craps is a game that involves dice. The game is played by rolling dice on the table. Some might use their skill to make sure they can manipulate the outcome of the throw, but most tend to throw and leave the rest to lady luck.
The same concept has been adopted in apps and mobile games. There is an avatar that represents the player. The player can control the avatar and play as if they were actually in an actual casino. Mobile games are now advanced and so they try to make the user experience as real and accurate as possible.