Recently, the study on the thermoelectric (TE) module has resurged due to the concerns about energy crisis and global climate changes. Thermoelectric (TE) technology enjoys a promising future to harvest and recover heat flow as being an alternative and environmentally friendly technology. In a conventional thermoelectric device, a junction is formed from two different conducting materials and convert electrical energy into heat energy for cooling and heating purposes. This review covers three parts, including the basic principle with current development, operation in cooling mode and thermal performance of thermoelectric module. The simplified energy balance equation for cooling and heating mode of thermoelectric module is also provided. Moreover, the modelling results of the given TEC module are presented based on the energy balance equation to show the relationship between its COP and temperature difference. Further real-life evaluations are needed to observe its thermal performance.