what is freezing mixture and where is it used?

Answer 1

A freezing mixture is a mix of solid and liquid, most often of ice and water, but can also be a molten metal that is solidifying. It has the feature of being exactly at the freezing/melting temperature of the material, especially if stirred, so can be used for maintaining that temperature for calibrating a measuring device or for a water bath for a chemical reaction.
The original zero point for the Fahrenheit scale was a freezing mixture of ice, water, and salt being the coldest sustainable point at that time.