A fuel cell converts chemical energy from a fuel into electricity through an electrochemical reaction. It requires a constant fuel source like hydrogen to continuously produce electricity. Fuel cells consist of an anode, cathode, and electrolyte. Protons flow from the anode to the cathode through the electrolyte, producing electricity. Fuel cells come in various types depending on the electrolyte used and stack together to increase voltage. They produce power efficiently but require a constant fuel source unlike batteries.