For me, communicating and feeling understood is one of the most pleasurable and rewarding things I can do with my time. It's unfortunate that I've met only a handful of people in my life that I can feel this way when talking with. This is the criteria I tend to use when judging the closeness of my friends and the intimacy of a relationship.
Something I have recently discovered is that my perception of someone else's understanding of me is often wrong, and being understood does not always mean feeling understood. For example, there is a person I know whom I often don't give enough credit for her understanding of what I say and the meaning of my behaviour - yet she constantly surprises me with the insight she has to why I do and say what I do. Understanding this mechanism is great, it let's me put the people I know into distinct groups: people I feel to understand me, and people I don't.
What I term "being understood" is really the feeling I get when I can verbalise raw thought and the other person will 'just get' the context and what lead me to say that - that 'click' when thought is transferred in as explicit a manner as possible with language.
The best part about this kind of interaction is the freedom of expression it allows, there are no taboos or things you need to avoid in fear of being 'taken the wrong way'. This feels comfortable and even the presence of a person like this improves my mood.
If you have any thoughts on this, email me!