Polarisation in the real world

Most light you see is unpolarised, but since reflected light is partially polarised, we can filter this out with polarisers to reduce the glare from the sun, or on wet roads.

TV signals are polarised by the orientation of the rods on the transmitting aerial. To receive a strong signal, you have to line up the rods on the receiving aerial with the rods on the transmitting aerial — if they aren't aligned, the signal strength will be lower, so the rods on TV aerials are all horizontal. It's the same with radio if you try tuning a radio and then moving the aerial around, your signal will come and go as the transmitting and receiving aerials go in and out of alignment.