What is heat Heat transfer Heat laws Daily lives

In the air, there are a lot of atoms and they are moving in different speed. The total average kinetic energy is the heat energy. So, heat means the movement of atoms. When it is hot, the atoms move faster and the spaces between them are large(p1). But when it is cold, the atoms move slowly and the spaces between them are small(p2).

p1. the spaces are large p2. the spaces are small

In same size area, the hotter area will have more air atoms then and the colder place. Because of that, a thermometer can measure temperature. The mercury or alcohol are very easy to move, so when the weather is hot, their atoms move very fast and the spaces between them are very large, it can so us the temperature. And some of the thermometer is starting with absolute zero.