Every person has three bodies.
Sthula sarira – your physical body. This is your flesh, your bones, your hair, your skin. This is the physical representation of the body that houses the “atman” or the “soul”. This is least significant. If you die, the sthula sarira is destroyed but the “atman” travels and finds another sthula sarira.
Sukshma sarira – your mental body. This is your thoughts, your knowledge, your experiences. This is how you imagine yourself to be. This is what you think yourself to be. It is just imaginary in nature and is not related with action/reactions of the universe. This is somewhat significant.
Karana Sarira – your causal body. This is your karma, your actions. This is how others see you based on not how you look but who you are and what you have done. This is what you are to the whole world. This is the most significant.
Human beings do not have an exact measure of their “Sukshma Sarira”. We cannot say with absolute measure who we are, it is because life is the journey where we are discovering ourselves (“Sukshma sarira”).
We have an imaginary notion of our existence in our head and we are mostly in love of who we imagine ourselves to be.
Mon: Who are you?
Man: I am John and I am an engineer.
Monk: I did not ask about your profession, Mister. I am asking about your existence.
Man: Uhm oh… I live in that street down there and I have a family of four.
Monk: I did not ask for your address and neither about your relationships. I am asking who are you?
Man: What does that mean who am I? I am a man, I work for this company and I live here. I love to play cricket , watch movies ….
Monk: Do you love yourself?
Man: Yes of course I do.
Monk: Why do you love yourself when you don’t even know who you are?
Man: What do you mean by I don’t know who am I? Of course I know myself better than anyone else.
Monk smiles and goes away.
So this man doesn’t know who he is. He has no idea about his “Sukshma sarira”, he imagines himself to be someone and is mostly in love with what he imagines himself to be.
Read – Three bodies doctrine and Subtle body