See the friendship page

The Facebook friendship page is a function that allows you to discover what two specific users have shared and have in common. The page shows the number of friends in common, along with photos, messages on their walls, events in which the two people both attended together, and the pages (they both like).
Everything is shown in a stream in chronological order, just like a profile.

To display the page of friendship simply type the following URL:

http://www.facebook.com/<ID Facebook 1>?and=<ID Facebook 2>   or

http://www.facebook.com/<vanity url>?and=<vanity url>