There are more ways to play Pokémon than ever before. While more and more Pokémon are added and new regions and mechanics are introduced, the core of the series remains intact. Capture Pokémon in the wild, raise them individually and as teams, and eventually you can become the very best like no one ever was.
One of the most important parts of raising and battling Pokémon is understanding their moves. A Pokémon can learn up to four moves. Many factors influence what moves a Pokémon can learn including type, breeding, and level.
The trainer has to decide what moves they want their Pokémon to know. Naturally, some moves are just better than others. Why make your Charizard use Ember when it can learn Flamethrower?