I would like you all to meet my pokemon named Evelon. She's an Eevee. I'm gonna let her explain Pokemon.
Pokemon translated is Pocket Monsters. They are called Poket Monsters because they can be caught by a pokeball shown here. These pokeballs can fit in your pocket. Hence the name. There are 150 known pokemon and probably more. Pokemon trainers like Ash
try to collect pokemon to battle against other pokemon trainers. There are other pokemon trainers who don't just want to battle pokemon but also to raise them.
Like Brock here. He cares for his pokemon and wants to be a great breeder. Some pokemon trainers will only collect a certain type of pokemon.
Misty only collects water pokemon. Their are certain types of pokemon. Normal, fighting, water, fire, electric, poison, flying, dragon, rock, grass, ground, ice, psychic, bug, and ghost (examples at the bottom). Pokemon all have levels. If a pokemon has a low level such as 3 it will do poorly against a higher level such as 26. To raise your pokemon up levels you must battle other wild pokemon or rival pokemon trainers.
Gary is Ash's rival. Both of them are trying to be the #1 pokemon master. They both must get badges from gyms to get into the pokemon leauge where you can become a pokemon master. When you start out you have to be 10-years-old. At this age you are a leagal pokemon trainer. You leave your friends and familiy to complete your dream. Most pokemon trainers wish to be a pokemon master or make it to the pokemon league. Some want to "Catch them all". This is where the goal is to catch all 150 pokemon. This task proves to be extremely difficult. Many pokemon are rare and hard to train.
Examples of the types of pokemon:
Tangula-Grass
Charmander-Fire
Squirtle-Water
Caterpie-bug
Pidgey-Flying
Clefariy-normal
Pikachu-electric
Ekans-poison
Manky-fighting
Diglett-ground
Abra-pshycic
Gastly-ghost
Onix-rock
Articuno-Ice
Dratini-dragon