A fuel cell is a device that turns fuel and air into electricity, heat, and other byproducts. This article focuses on hydrogen fuel cells, specifically proton exchange membrane fuel cells (PEMFCs) and solid oxide fuel cells (SOFCs). It discusses different types of fuel cells based on factors like electrolyte operation and temperature. Fuel cells need additional components to work, forming a fuel-cell system. They have a wide range of applications in mobile, stationary, and transport settings.