Most people understand that winter tyres are designed for the cold winter and summer tyres for the warm summer weather and not vice versa. Summer tyres should just not be used in the winter as they cannot perform well when the temperatures drop below zero. The main problem with summer tyres during the winter period is that when the temperature drops below zero, the rubber in the summer tyres becomes hard and inflexible. The hard rubber is not able to give you the necessary traction that you need to handle your car on wintry roads.
A hard rubber tyre is not able to conform to the road surface and will remain hard and inflexible. This is not what you want when you are looking for optimal grip on slippery surfaces. This is why winter tyres are made out of a completely different rubber compound. They are made out of a compound that is made to remain flexible and soft even in the very cold winter temperatures. This ensures that they are able to grip the slippery surface.
In addition to the special rubber compound, winter tyre has a tread design that is made to create traction on snow and ice and to be able to remove slush in order to remain in contact with the road surface. Winter tyres can have metal studs protruding from the tread. These tyres are referred to as studded tyres. Or you can have tyres that use the tread design and other technological innovations to create the needed traction. These are referred to as non-studded tyres.
Both these tyre options are able to create sufficient traction on ice and snow. If a tyre is meant for winter use, it should be also officially approved for winter use and have a winter-approved symbol on the sidewall of the tyre. This symbol is in the form of a mountaintop with three tops with a snowflake inside it. If your tyres have this symbol, then you know that they are safe to drive with during the winter. When the winter ends, remember to switch back to your summer tyres because winter tyres do not perform well in warm temperatures.