From what I have understood, if a physical system may be in one of many configurations then the most general state is a combination of all of these possibilities. However, when you measure that physical system, you will get one of these possible states.
I have also read that a photon polarized along the direction $\alpha$ can be written as a superposition of the two states 1) polarization along the x direction and 2) polarization along the y direction. When you measure the photon polarization, you can get a combination of these 2 states (x and y), not only one of the states (x or y). It seems like this explanation of the photon polarization goes against the concept of quantum polarization.
If the explanation is that when you measure, you can also get the superimposed, then how can, say, an electron be in the superimposed state of spin up and down, if you can't measure that electron and get a state of spin up and down at the same time?