Question

What is thermal equilibrium

Answer 1

The condition under which two substances in physical contactwith each other exchange no heat energy. Two substances inthermal equilibrium are said to be at the same temperature. Seealso thermodynamics. 

Answer 2

A higher temperature object which is in contact with a lower temperature object will transfer heat to the lower temperature object. The objects will approach the same temperature, and in the absence of loss to other objects, they will then maintain a constant temperature. They are then said to be in thermal equilibrium.