They know you enough to feel safe making a mental model of you and using it to predict you. That's a different point for different people--I certainly don't think/feel/sense that I know you well enough to make a mental model, let alone use it to predict your preferences or behavior.

I second the commenter above who distinguishes between friends and casual acquaintances. I wish we had a better descriptive term for that in English, but then I also wish I knew better how to move from the casual acquaintance stage to the friend stage (and sometimes on into the close friend stage).