It's basically a safe space for each of you to state how you see things, without being interrupted: the counsellor mediates and ensures that each person is listened to in turn.
Then the counsellor will say for example, "X said Y - how would you respond to that from your point of view, Z?" After which X really listens (if their heart is in the counselling in the first place) to Z's feelings and asks themselves for example "Is Z saying something I can understand? Where/how/ do, our memories of the event differ?"
The premise is that by stopping oneself from not listening properly, because instead we're so busy thinking of our own outraged response to something that upsets us, we'll actually "HEAR" how the situation appeared to, and how it affected, the other person.
The counsellor is always ready to stop someone talking over another instead of listening and evaluating; they will question you to see if what e.g., "Z" said made you see the difference between your two expectations; made you aware of how your own actions or words made "Z" feel, and if you see what you did or said any differently now that the reception of it has been explained to you.
It may sound simple, but if you go into it really meaning to find a way through the maze, it can be hard, tearful work.
The flip side is, it can give you a whole new perspective on things, and heal a lot of hurts and bitterness.