It is the act of sharing what is inmost in yourself with another. Experiencing intimacy is being included in another self concept.
Intimacy exemplifies itself in what is called the attribution process.
This is a tendency to attribute our behavior to others internal factors. This is less pronounced if the other seems to be intimate with the self. A lower distinction between self and other is apparent when allocating resources as opposed to those who are not intimate. For example, those who are intimate can share food at the dinner table, but you would not do this with a new acquaintance. Those in close nit relationships tend to share a transactive memory.