Food, water, and energy represent the fundamental requirements of human society, and their interdependence forms a critical relationship often referred to as the food–water–energy nexus. Among these components, energy plays a vital role in maintaining life, supporting technological progress, and driving economic development. However, the rapid growth in energy demand, along with the depletion of conventional resources and increasing environmental concerns, has led to significant global challenges, including energy shortages and ecological degradation. In this context, thermoelectric energy conversion has gained attention as a promising approach to addressing these issues in the modern era. Thermoelectric systems have the ability to directly transform heat into electrical power through the Seebeck effect, which makes them particularly useful for recovering waste heat and enabling distributed power generation. This paper presents an overview of thermoelectric technology, highlighting its operating principles, importance, and the classification of thermoelectric generators (TEGs). Additionally, the study examines the materials utilized in thermoelectric devices, focusing on their thermal and electrical characteristics, as well as their impact on system efficiency. Recent developments in advanced materials, including semiconductor-based and nanostructured compounds, are also discussed due to their significant contribution to improving energy conversion performance. The paper further explores key design aspects and optimization strategies aimed at enhancing the effectiveness of TEG systems. Various applications of thermoelectric generators are reviewed, such as their use in industrial processes for waste heat recovery, automotive technologies, space exploration, and small-scale energy systems. These examples demonstrate the flexibility and growing importance of thermoelectric solutions across multiple sectors. Finally, the paper identifies existing limitations and outlines potential directions for future research in thermoelectric power generation. Emphasis is placed on improving material performance, reducing production costs, and developing more efficient system designs. Overall, thermoelectric technology offers a sustainable and environmentally responsible pathway to help mitigate current energy challenges.