How do winter tyres work?

Snow, ice and sub-zero temperatures – winter has a few unpleasant surprises for motorists up its sleeve. Winter tyres are mandatory in countries such as Sweden or the Czech Republic in order to drive safely in winter. They are more wear-resistant, offer better grip and ensure safer steering. What makes winter tyres different and how do they work?

Barum. A brand of Continental.
Good tyres. Good deal.