This is a very interesting question. Each button on the remote control has a certain code. When you push the button, the code is sent from the remote control to the TV by something called infrared light. Infrared is a type of light that we can't see with our eyes, but the TV can recognize. The TV will then see the code that the remote control sent and perform the button's command. So when you push the increase volume button, the remote sends the code for increase volume to the TV, which then reads the code and increases the volume.

A TV remote control sends out beams of light that are invisible to the human eye. The light beams go out in short pulses, and depending on what you want to do with the TV (for example, turn the volume up or increase the channel number), the remote will send out a different number of pulses or length of pulses that signal the TV to do that specific command. A receiver on the TV reads the light pulses, which is why you have to aim the remote in the direction of the TV.

The same way light travels from a light bulb to our eyes, light travels from the remote control to the TV set. ​Unlike the light bulb though which we can see, not all the light is visible. Actually, we, humans, only see a small part of the spectrum, of the range of light, from blue to red. Snakes and bats can see light that is further than red, called the "infra-red". It is the same light that fast food restaurants use to keep burger patties warm after they cook them.

Because the technique is based on light, you need to be pointing the control towards the TV set and you cannot change channel if you are behind the wall : because the light cannot pass. When you press a button of the remote control, a series of light pulses get emitted and reach the TV set directing it what to do.