Thermoelectric devices exploit the Seebeck and Peltier effects to directly convert temperature differences into electrical energy and vice versa, offering a unique solution for power generation and solid-state cooling. These devices are based on materials with a high thermoelectric efficiency, which depends on optimizing the electrical conductivity, thermal conductivity, and Seebeck coefficient. The absence of moving parts makes thermoelectric devices reliable and environmentally friendly, suitable for applications ranging from waste heat recovery in industrial settings to precision cooling in electronics and medical devices. Despite their potential, challenges such as material cost and efficiency need to be addressed to fully realize their promise in sustainable energy technologies.