Here are the basics of Pokémon:
Shiny Pokémon are Pokémon which are a different colored Pokémon and is really hard to come by, they are sought after by collectors and trainers.
This is a legendary Pokémon, a Pokémon that is one-of-a-kind (We aren't talking about Pokémon games). They sometimes have unique powers, like Dialga has Roar of Time, and Palkia has Spacial Rend, not Special Rend, Spacial Rend.
This is a starter Pokémon, a Pokémon given to you by a Pokémon professor. You can receive different kinds depending on your location and your choice.