If two junctions of a thermocouple are kept at different temperatures, a direct emf is developed in the thermocouple and as a result, a direct current flows through it.
This effect was developed by a German Scientist Seebeck in 1821 and is called the Seebeck effect. The emf so developed is called the Thermo emf and the corresponding current in the thermocouple is termed a thermoelectric current.
When a current is sent through a thermocouple, depending on the direction of the current, heat is evolved at one of the junctions which is thus heated while heat is absorbed in the other junction which is cooled. This effect was discovered by Scientist Peltier in 1834 and is known as the Peltier effect.