For Christians, the soul is an integral part of who you are. You have a body and you have a soul and the two are connected. Even if they don’t believe in the resurrection of the body, most Christians, in fact most Americans, believe in the immortality of the soul.
Even if you’re not religious you probably refer to the soul as a sort of fluffy spiritual term for your personality or even just a euphemism for “a life”: maybe you’ve bought Chicken Soup for the Soul or offered to sell your soul to Satan. Souls are a part of pop culture as well as religious belief. But, leaving aside religion, what is a soul, exactly? Is it some kind of immaterial ghostly stuff that is only accidentally attached to the body? Or is it more substantial? And if it is, of what is it made? And where is it in your body?
Christianity did not invent the concept of the soul, but, like many other things, it inherited it from Greek philosophy. For Plato the soul was the better half of the two parts of the human person. There was there body, which was cumbersome, temporary, and decaying; and then there was the soul (psyche), the invisible seat of wisdom, which was immortal and effectively trapped by the body until death.