Shiny pokemon are pokemon of different colors than normal (shiny rayquaza is black instead of green, shiny metagross is gray and gold instead of blue and silver, shiny charizard is black instead of red).
these pokemon are EXTREAMLY rare.
every time you see a wild pokemon there is a 1 in 8,192 chance that the pokemon will be a shiny pokemon.
shiny pokemon are alot harder than there normal versions.
despite this shiny pokemon have lower stats than their normal versions.
you can use the pokeradar key-item in the grass, if the grass shines any other color than gold......it's a shiny pokemon.