The salt that melts ice is called rock salt or halite. It's primarily sodium chloride (NaCl), the same compound found in table salt.

Here's how it works:

* Lowering the Freezing Point: When salt dissolves in water, it disrupts the formation of ice crystals. This lowers the freezing point of water, meaning it needs to be colder than 32°F (0°C) for the water to freeze.

* Melting Ice: If the temperature is above the lowered freezing point, the ice will start to melt.

It's important to note that while rock salt is effective at melting ice, it can also have negative environmental impacts.

Let me know if you'd like to know more about those impacts!