a shiny pokemon is basically a really rare version of a pokemon. chances are like 1/8000 of a chance of finding them in the wild, they typically have a differnet color set then its origaanl form, although being shiny doesnt affect its abilites. +the question was not at all stupid, in fact i was quite bewildered myself when i found out about them.
I got 1337 hax, you don't, deal with it.