Suppose you have following Profile Picture.
Following is URL of above Image
In this Profile Image URL, there is Id i.e. 1438566719. This is Facebook Profile ID.
From this facebook ID, we can get the facebook profile URL.
Following is facebook profile URL.
You will set it will automatic redirect to https://www.facebook.com/arun.compute.
In Facebook, every things have ID whether it is profile URL, Page OR APP.
when you open http://facebook.com/[ID_NUMBER], It wil be automatic redirect to its specific page.