In reading the Genesis account of when God created the first man we learn what is the essence of a human being. At least the way God originally intended man to be.
In the beginning:
1)God said, Let Us make man in Our image, in Our likeness.
2)So God created man in His own image; in the image of God He created him; male and female He created them.
3)God formed the man from the dust of the ground.
4)He then breathed into his nostrils the "breath of life" (being the Holy Spirit).
5)Then man became a living soul.
So from this we learn that man is a spirit, brought forth from the Holy Spirit who is life w/in us. As spirits living in the earth, we live w/in a human vessel; a physical body made from the earth. In order to function in a physical world. Having the "breathe of life" within us is also, what gives us our identity as one who bears the "image and likeness of God". The image that God desired to be multiplied throughout the earth. But this is what was lost when man fell into sin.
We also, have a soul. Although, man was originally intended to be one in spirit w/God and one another by His Spirit, we each have a soul giving us our individuality. Our difference in personality, feelings, opinion, taste, intentions and will is an expression of our souls. Like w/everything we see in the creation, God wanted variety also, amongst us.
Now every human being has a body, a spirit and a soul. But not every human being has the "breath of life". Only those who have repented of their sinful nature, choosing to surrender to the will of God. In the process, receiving the indwelling of the Spirit of God (who is life), who in turn along w/the word (the Bible) direct our souls, hearts, and minds in our new life and walk w/God.
As for those who DO NOT walk in repentance, not having the Holy Spirit, life is not present w/in them. They're alive in the natural sense. But spiritually are dead. Remaining disconnected from God.
When you die, your body returns to the dust from where it came, but your spirit and soul continue...either in heaven or hell. It is because we have a soul that whether we are in body or in spirit we continue to have our individuality.