What Does Temperature Measure?
Temperature measures particle velocity, body temperature, the average kinetic energy of molecules and the behavior of thermometric material. Temperature also controls the direction of heat transfer between bodies.
The temperature of a body that does not exchange energy with its surroundings remains spatially uniform. When a path that allows heat to pass through from one object to another is open, energy transfers spontaneously as heat from a hotter body to a colder one. However, if the path exists and not heat flows between the two bodies, it means that they are equally hot and are at thermal equilibrium.
This means that there is no longer transfer of energy between the bodies, which means that they are at the same temperature. Therefore, both objects are in their own states of internal thermodynamic equilibrium, which means they obey the Zeroth law of thermodynamics.