If you sprinkle salt on some ice, you can melt it. This is because the salt dissolves in the liquid water that coats the ice, and so lowers its freezing point.
This is why in winter, the councils sprinkle stuff on the roads and pavements. It’s called grit, but is actually made of “grit” (dirty rock salt) and salt (just pure salt). The salt lowers the melting point of the snow causing it to melt as described above. The grit part increased the friction between tyres of vehicles (or your feet!) and the road (/pavement).
You can still freeze salty water, but it needs a lower temperature!