What does sleet mean?

When the temperature is zero, the falling object is a mixture of rain and snow, which is called sleet.

It is rain when the temperature is above zero, and snow when the temperature drops below zero, so it is called rain and snow after rain.

Snow is the crystallization of water. Clouds in the sky encounter cold air, the temperature drops, and water vapor forms ice crystals under the combined action of low temperature and tiny dust. The volume keeps increasing. If the density exceeds the air, it will drop, indicating that it is snowing.

It usually doesn't snow in a clear sky. But because of the different clouds, one layer is snow and the other layer is rain, so sleet will form.