It’s made of emotion. The “soul” is the “feeler”, it is the source of all human emotions. It is the source of all love and beauty, but also all hatred and ugliness. It is also sometimes called Atman, “consciousness” or “God”. It is ephemeral, non-physical. In self-realization one often takes the identity of the soul and literally “becomes” consciousness. One could then say “I am not my body, I am consciousness” or “I am a soul in a body”. The soul is the source of the feeling of “I am”.

It is usually discovered when the egoic identity falls away. Once discovered, the soul begins to suffer, which is why after self-realization people can become very sensitive, naked, emotional. Everything hurts. Tears out of the blue. All of that comes out. It is the soul’s ultimate destiny to completely surrender to The Absolute and become non-existent along with the ego.

You could say ego is the “thinker” and soul is the “feeler”, so first the thinker goes away and then the feeler.

But you could also say that both constitute ego and in self-realization only the core of it is gone, and throughout the successive journey to enlightenment the rest of it goes away. Then you don’t need a special term for “soul”.

Both interpretarions would be correct, it doesn’t matter.