Generations

1. Generation I

   Kanto · Red, Blue, Yellow, FireRed, LeafGreen

   The original 151 Pokémon and the type system. A single Special stat (no split Sp. Atk/Sp. Def).

2. Generation II

   Johto · Gold, Silver, Crystal, HeartGold, SoulSilver

   Held items, breeding and eggs. Day/night cycle and the new Dark and Steel types. Split of Special into Sp. Atk and Sp. Def.

3. Generation III

   Hoenn · Ruby, Sapphire, Emerald, FireRed, LeafGreen

   Abilities and Natures. Double Battles and modern EV system.

4. Generation IV

   Sinnoh · Diamond, Pearl, Platinum, HeartGold, SoulSilver

   Physical/Special split moved to per-move. Online Wi-Fi battling.

5. Generation V

   Unova · Black, White, Black 2, White 2

   Fully animated battle sprites. Triple and Rotation Battles.

6. Generation VI

   Kalos · X, Y, Omega Ruby, Alpha Sapphire

   Mega Evolution. The Fairy type and full 3D graphics.

7. Generation VII

   Alola · Sun, Moon, Ultra Sun, Ultra Moon, Let's Go Pikachu, Let's Go Eevee

   Z-Moves. Alolan Forms (regional variants).

8. Generation VIII

   Galar / Hisui · Sword, Shield, Brilliant Diamond, Shining Pearl, Legends: Arceus

   Dynamax and Gigantamax. Galarian and Hisuian Forms.

9. Generation IX

   Paldea · Scarlet, Violet

   Terastallization (changes a Pokémon's type in battle). Fully open-world exploration.