Fermi energy is a concept in quantum mechanics that describes the highest energy level occupied by electrons in a solid at absolute zero temperature. It is named after the physicist Enrico Fermi, who contributed significantly to the understanding of electron behavior in materials. The Fermi energy helps determine the electrical and thermal properties of metals and semiconductors. In metals, the Fermi energy is typically located within a band of energy levels that electrons can occupy. This energy level plays a crucial role in understanding phenomena such as electrical conductivity and heat capacity, as it influences how electrons move and interact within the material.