the free soul is rare, but you know it when you see it - basically because you feel good, very good, when you are near or with them.

The phrase “free soul” is referring to someone who is independent and open-minded, and is not influenced by other people or society. These types of people are rare, but you know it when you come across them. Being around them will make you feel a natural, deep and good feeling; the kind of feeling that makes you feel content and relaxed.