The next morning dawned cold, and clear, and trees were literally shredded. Overhead flew a group of national guard helicopters, literally the only thing moving anywhere. You would have thought we had been at war. Instead, this was the aftermath of the Great Ice storm of 1998. Freezing rain is a form of precipitation, and certain conditions have to be met to generate moisture from the sky, and have the moisture fall in the form of freezing rain.
Freezing rain is a specific form of precipitation, as is rain, drizzle, sleet, and hail.
It is the result of water particles falling as snow, then encountering a layer of warm air where the particles melt into rain. However, before the rain hits the ground, it goes through a cold layer of air just before the surface of the ground. When these supercooled drops hit the ground, they thin out and freeze, instantly, forming a thin film of ice. Both types, however, can be deadly. But the real danger with freezing rain is the build-up of ice on trees and power lines.