When salt is added to water, it raises the boiling point, requiring the salt water to reach a higher temperature to boil. The boiling point increases as more salt is added to the water.
Chefs use salt to raise the boiling point of water, since the higher temperature of the water reduces the cooking time. Salt is used on icy sidewalks because it lowers the freezing point of the water and causes the ice to melt. Science refer to the principle of salt raising the boiling point and lowering the freezing point of water as the colligative property of solutions.