It's pretty obvious this is about some form of a relationship that is forbidden in some way. Maybe someone doesn't approve of it. Even though the relationship is not allowed, the people involved see each other in secret, hiding their feeling until they are only with each other. They are there own secret, hidden away from the world, hence the nobody sees, nobody knows. And when they are together, they "uncover" and show their true selves because they know the other accepts them and loves them just how they are.
It's pretty obvious this is about some form of a relationship that is forbidden in some way. Maybe someone doesn't approve of it. Even though the relationship is not allowed, the people involved see each other in secret, hiding their feeling until they are only with each other. They are there own secret, hidden away from the world, hence the nobody sees, nobody knows. And when they are together, they "uncover" and show their true selves because they know the other accepts them and loves them just how they are.