From Bulbapedia, the community-driven Pokémon encyclopedia.
Pokémon figures are figures that the player uses to battle in the Pokémon Trading Figure Game.
The figures are made by Kaiyodo, a famous figurine and sculpture company in Japan. This is the same company that made the Giratina figure for pre-ordering Pokémon Platinum, the Lugia and Ho-Oh figures for pre-ordering Pokémon HeartGold and SoulSilver, and the Arceus and Entei figures that appeared in Pokémon Trading Card Game gift sets.
Certain figures, such as pearl figures and crystal figures are considerably rarer than others. Pearl figures feature a soft sheen on white plasting, while crystal figures are transparent. Only Super Rare figures, such as Charizard are capable of having the crystal rarity; likewise, only rare figures are capable of having the pearl rarity.
Many of the Pokémon Trading Figure Game figures were never released. The TFG was canceled after the starter sets of Groundbreakers were released exclusively at Wal-Mart. There were supposed to be at least three sets of these figures, but only Next Quest was released in its entirety.
For a full list of figures, see here.