Pokémon is short for “Pocket Monsters", the original Japanese name.
26 February 1996 marks the debut of the Pokémon franchise in the form of both those games on the Game Boy in Japan. At its heart, Pocket Monsters: Red and Green was a very basic Japanese role-playing game. You play as a Pokémon trainer travelling the world and collecting the ubiquitous little monsters (inspired by Tajiri’s childhood love for insect collection) and training them in battles with other Pokémon.
You start out with a single Pokémon (you get to pick one of three) and one aim is to “Catch ‘em all". To get all 151 Pokémon, however, you had to trade with other players.