The Soul is basically the mind, with extra religious bullshit thrown in.
It is something imaginary that religious folk try and say you have. It's some sort of thing that somehow carries on your existence after you die, or something. There's no physical evidence that immortal souls exist. First Christians try and comfort you and tell you, "When you die you'll be with Jesus, all Christians do that."
There's no evidence for heaven, for hell or for any soul, Freethinkers just think we should concentrate on making this life as good as possible for ourselves and for other people because this life is the only life we know about.