Isn't it slippery?
Yes. That's why I have 35mm wide knobby tires with 106 carbide tipped studs.

Do you ride on the road?
Yes.

Isn't is slushy and hard to pedal through snow?
Sometimes. Other times I'm out before the plows and it's 4" deep fresh snow. Other times the cars have packed it down and it's a sheet of crunchy snow, or wet slush-ice. It's certainly not as easy as riding in the summer.

Don't cars slide into you breaking every bone in your body in a cold, wet tragedy?
Not yet.

Could somebody explain to me how this works?
I wear extra layers to stay warm. I leave extra time to account for the drop in speed. I pay extra attention to what's going on around me. I change my route to exclude some of the busier narrow roads I take in the summer.