What does polarized on sunglasses mean?

[Silverdale]

I have found polarized and unpolarized on the sunglasses. What does it mean and what's the difference? Which one is better?

[Lindenau]

Polarized lenses can protect our eyes from the damage of UV rays. Polarized lenses can change the way light hits our eyes. Polarized sunglasses can give us a clearer view and eliminate glare, this will make our eyes feel more comfortable. Usually they are an excellent choice though they are much more expensive than unpolarized sunglasses, but they have better quality.

[Silverado]

I think the polarized sunglasses are better. I have bought two pairs of sunglasses, one is polarized and the other is unpolarized. The apparent difference between them is that polarized sunglasses are more expensive than the unpolarized one. Haha, I also think that the polarized one is more delicate. But the seller told me that the polarized one can reduce the annoying and dangerous glare and prevent our eyes.