The technical term is dielectric glass.That is not your standard glass or mirror which is glass with a reflective surface applied to the rear. Mirror glass is specially engineered material with the correct properties to control the way the light flows through the glass and is reflected on it. The special material is applied in layers on a glass base until the correct polarization tuning is attained. If you are interested in mirror TVs then obtain a sample available from some manufacturers and test it out yourself. The sample will look just like a normal piece of glass, especially if you hold it up to the light. With your TV on hold the glass in front of the TV and you should be able to see the mirror TV picture clearly through the glass. With the TV off you should get a reflection of what is in the room. Most of these kinds of mirrors do not work well close up, stand away from the mirror to assess how well it works. The amount of light in a room can also affect how well the mirror tv work. For good reflection you need lots of bright light, but for the mirror TV picture to show well, you need low levels of room lighting. If you can adjust the lighting when you watch TV you will get a better effect. With your sample play around with the position you hope to have the mirror TV in and the room lighting to ensure that you will get the best result from your mirror TV.