Transcript:

Why can two identical photons occupy the same location in space, whereas two identical electrons cannot? 

So the easiest way to answer this is to recognize that if you plot the wave function of two identical particles separated by a distance x, so the x-axis is the separation between the identical particles, then either the wave function is even like it is shown here or the wave function is odd like it is shown here. 

Now, there is a fundamental difference between a photon and an electron. A photon is what is called an integer spin particle, and the electron is a half-integer spin particle and the spin-statistics theorem says that integer spin particles will always have an even wave function, whereas half-integer spin particles will have an odd wave function. 

So now, look what happens if I reduce the separation distance to zero for a photon: you have a non-zero probability, which means two photons can exist at no separation. But if I make the distance between two electrons zero, then the probability of that happening is identically zero, which is why two identical electrons can never occupy the same location in space, whereas two identical photons can. It's as simple as that.