Just my own thoughts, really.
It's virtually impossible to "describe" a soul but here's one way to conceptualize it. A soul is the spiritual, divine energy that animates us. You can't see it or touch it, much like you can't see or touch sound. Our souls are part of God, and are the divine part of us. It's the part that makes our "mind" and personality, it's our identity, thus making it something that exists beyond physical matter. It's the part that makes us self-aware and sentient.