The Purpose for the Unown

I wonder what's the purpose for the Unown in the Pokemon universe?

I think in one of the old pokemon games the unknown were used as the alphabet to get a certain pokemon. There was like a tablet on a wall and you couldn't understand what it said unless you used the unknown or something like that.

Yea, I kinda figure as much that the Unown is used to solve ancient riddles or mysteries which can lead to different or extraordinary things in the Pokemon World.

Yea i never understood those either and just watching them fly by on the screen was no help either its just like one of them unsolved mysteries.