Thermal engines are machines that convert heat energy into mechanical work. They operate on the principle of converting thermal energy, usually from burning fuel, into motion. Common examples include internal combustion engines found in cars and external combustion engines like steam engines. These engines typically follow a cycle, such as the Otto cycle or Rankine cycle, to efficiently produce energy. The efficiency of thermal engines is influenced by factors like temperature differences and the type of fuel used. While they are widely used in transportation and power generation, thermal engines also produce emissions, leading to environmental concerns. Advances in technology aim to improve their efficiency and reduce their impact.