Quantum gas refers to a state of matter formed by particles that obey the principles of quantum mechanics. This includes two main types: Bose-Einstein condensates and Fermi gases. In a Bose-Einstein condensate, particles called bosons occupy the same quantum state, leading to unique properties like superfluidity. Fermi gases, on the other hand, consist of fermions, which follow the Pauli exclusion principle, meaning no two fermions can occupy the same state. These gases exhibit behaviors that are crucial for understanding phenomena in condensed matter physics and have applications in fields like quantum computing and superconductivity.