Dice (or number cubes) are used in our classrooms to explore numbers. We use them for games, for examining patterns of random numbers, and more. A die (traditionally) is a cube with circular "pips" on each side representing a number. The pattern on dice is the same so people learn to associate the pattern with the number. Each value on a die is equally likely to appear (as shown by our repeated activity called Dice Roll and Tally.) So we practice counting, equally likely outcomes, and many other "number sense" concepts with these tools.
Another exploration we use regards the patterns of totals that two dice can represent. It is interesting to hear their theories of the "shape" of this chart before and after we begin!