Microbial fuel cells (MFCs) have been on the frontline in the quest for sustainable energy solutions and new mechanisms for environmental remediation. This chapter embarks on the complex world of MFCs, covering basic principles governing their operations, the key roles played by bacteria and biofilms, and the complex electron transfer mechanisms conducting power generation. We have tried to unravel the physiology and metabolism of anode respiring bacteria (ARB), strategies for enhancing their performance, and microbial processes driving cathodic reactions. We have attempted to explore in detail environmental factors formulating bacterial generation of electricity, comprehensively the consequences and impact of temperature, pH, salinity, and substrate types, pointing out their inferences for engineering focus and technological improvement as well as innovation. Specifically, the understanding that will be derived from this overview chapter makes it quite clear how such conversion of organic waste materials into electricity will have the dual benefit of minimizing the energy needed for energy-intensive conventional wastewater treatment methods and avoiding the greenhouse gas emissions linked with them.