(I called them see through mirrors because I don't know what their actual name is)
I have seen a lot of pictures of glass-like materials which reflect light from on side, and from the other side, they transmit light.
What i want to say is - Let side A and side B be the two sides. Side B will reflect all (almost all) the light falling onto it. Side A will allow the light to propagate through the material towards the other side. So in a sense, side B acts like a mirror and side A acts like a transparent glass. This means that if you fit this material into the window of your room, you can see the outside but the people outside can't see you (those people can see their own reflection).
So the question is-
How is this even possible? And more importantly, What are these things made of?