one dimensional Schrödinger equation: $$ \left[-\frac{\hbar^{2}}{2 m}\frac{\partial^2\psi(x)}{\partial{x}^2} +V(x)\right] \psi(x)=E \psi(x)$$
I know that to calculate the eigenfunctions $ \psi(x) $ depends on the potential $V(x)$, but in general, which are the characteristic of $\psi(x)$? it can be a complex function or a real function and how proof that?
What means that $\phi(x)$ is a physical solution if we also care about the probability?
Can unphysical wavefunctions give a right probability?