The [dice] tags are a simple random number generator, implemented by JEEP in October 2004 and re-implemented in May 2011 after the change of host.
Will roll a Y sided die, X times. X must be less than 200 and Y must be 100 or less. If you chose to roll a 100 sided die, it will be represented as if you rolled two 10 sided dice, with one being the tens digit and the other being the ones digit.
The result will be something like:
Original Roll String: 2d6 6-Sided Dice Results: 1, 5 (Total = 6)
Note this this is not fool proof. People can edit their posts and get a new dice roll. It will usually say FIXED, but this is not foolproof either. If you are in a forum where people can edit their posts, you should pay close attention and/or only play with people you can trust.
You can also use simple math operators (+, -, *, and /).
Original Roll String: 2d6+4 6-Sided Dice Results: (1, 5) + 4 (Total = 10)
Use in random voting
Since its introduction, one use of the [dice] tag has been to choose a target for a random vote at the beginning of a game. Recently, it has become objectionable to some Scummers to do this, because it destroys any purpose or analysis on the "random" vote by assuring that it is 100% meaningless. More information can be found in this thread.