Who am I

What distinguishes me from the person across the road or the one I met in Sainsbury's yesterday. It isn't the body since my body is much the same as anyone else's given my age a little less wear and tear or a little more, but largely we are governed by the same or similar mechanical features such as heart beat, lungs inhaling and exhaling, all the organs doing what ever they do but each body of each person is roughly the same. Our brains are also much the same. Some seem to have developed faculties which provide us with the tools to excel in certain things but on the whole our brains are much the same performing the same tasks. What is it then that defines me.
The me that I think about when I "think" of myself. 

The brain has within its electrical impulses and millions of synaptic connections a thing we call the mind and its this thing called the mind which identifies us. From the mind we have a sense of our position and perspective of everything else we can know and our relationship to that which we know. Much of what we know is an amalgam of what we sense and see mixed in with a memory which refers us to what we had understood at a time in the past when a similar event occurred. We rationalise that event and its outcome with the current one and expect the same to happen. When it doesn't we assimilate both experiences to give us wider options as what to do and think in the future if the same thing happens again.
In a broad sense this is called experience and our understanding of life is based on our experience.
So in a way our mind is fed its signals from the stimulus around it and it makes sense of that stimulus from the memories we have stored from moments past.
Our individuality comes from those moments past since without their reference we would be faced with a uniquely new set of cognitive experience which would have no meaning. Not having meaning our reaction would be unpredictable and it's the predictability which makes us who we are and identifies us from others.
Clearly there are pools of similarity but each with their own unique path, each person treading a separate path depending on their exposure to this and that, then in small but special ways, we are all different.