I can't remember if I've ever posted this here, and because my next post is dependant to a certain extent upon the analogy, I'll refresh your mind.
Friendship is much like a medeival castle. Every person is the master of a castle, including a keep, a courtyard, and the town surrounding the defensive structures. As we meet people throughout our lives, they travel into our town. The friendly strangers, the acquaintances, the friends of friends, they all 'live' in the town: the lord or lady of the castle is aware of their presence, and tolerates any activities, strolling players, etc. within the outskirts of the city.
But sometimes, there are exceptional strangers. They're interesting, unusual, or show friendly intent. And so, as the owner of the castle, we invite them into the courtyard of the castle. They're through the portcullis, the outerwall, the outer defenses. There are less people in the courtyard, obviously. These are the friends of the owner of the town. Not necessarily good friends, but ones trusted *enough* to get through the first layer of archers, pikemen, and boiling lead. The lord or lady of the castle interacts with these people more often, many times going out to visit and socialize with the inhabitants.
And sometimes, if a particular visitor impresses the lord or lady of the manor, they'll be invited in the keep. There are no defenses up now, and it's pretty posh inside. These are your or my intimate friends. The ones we trust so much, we open up to them. Sometimes, they move back to the courtyard for a time, but they stay close.
Like it? I do.
Now, on to the post this is relevant to.