A tool intimately familiar to human history, used in matters of gambling since the dawn of time.
TRPGs offer a roleplaying experience in analog form, so dice are essential to add an element of randomness to the affair.
The most common type has six sides, but TRPGs often utilize dice with eight, ten, twelve, or twenty sides. On occasion hundred-sided dice that are effectively spheres that roll forever are used. Other times, four-sided pyramids can fall onto the floor and cause a painful catastrophe later down the road.
A commonplace notation for dice rolls is “xDy,” where D represents dice, the first number the number of dice and the second number the type of dice. Thus, 2D6 is equivalent to rolling two dice that have six sides each.