Thermal equilibrium  refers to temperature.The temperature within the system is spatially and temporally uniform. It is a relation between the physical states of 2 bodies means that there is actual or implied thermal connection between them,through a path that is permeable only to heat, and that no energy is transferred through the path. This technical sense is concerned with the theory of definition of temperature

USE: To prepare bodies with separately uniform temperatures then put them into purely thermal communication with each other
 thermal equilibrium is used sometimes in the common parlance of the ordinary language of physical discourse, and sometimes as a specialized technical term in thermodynamics