Pokémon Diamond Version, Pearl Version, and Platinum Version - Individual Values
Individual Values, or IVs, range from 0 through 31. These values can differ between two Pokémon of the same species and define a particular Pokémon's stat potential rather than the stat potential of its species. There are six Individual Values for Attack, Defense, Special Attack, Special Defense, Speed, and HP. A Pokémon begins with randomly determined Individual Values.
For a level 100 Pokémon, each Individual Value contributes that many stat points to the corresponding stat.