Yes salt is supposed to be put down on the pavement and sidewalks, driveways etc before the snow falls.
The salt helps to keep the snow from sticking to the surface and helps keep ice from forming and melts any ice that is there when you put the salt down.
So if you expect ice and snow or even just ice or just snow put the salt down on the surface such as your sidewalks, driveways, etc before the ice or snow occurs.
That helps to keep the snow and ice from sticking and causing slippery surfaces.
However in a major snow storm the snow could still pile up but it makes it easier to get rid of the snow.
I always use a snow blower when the snow gets too bad and it makes it easy to get rid of snow and the salt I put down keeps the surfaces from getting slippery.