Explain the significance of `Psi` and `Psi^(2)` ?

Explanation

A moving electron is associated with a wave and wave function `Psi` gives the amplitude of electron wave. It has got no physical significance. Therefore the square of `Psi` i.e., `Psi^(2)` has a physical significance. In electron wave, `Psi^(2)` gives the intensity of electron at any point.
In other words `Psi^(2)` helps in assessing the probability of electron in particular region, Thus `Psi^(2)` is called probability density and Y is called probability amplitude.