T_c, or the critical temperature, is the temperature below which a material exhibits superconductivity. Superconductivity is a phenomenon where a material can conduct electricity without resistance, allowing for efficient energy transfer. The value of T_c varies among different materials, with some superconductors operating at higher temperatures than others. The discovery of high-temperature superconductors has sparked significant interest in the field of condensed matter physics. Researchers aim to understand the mechanisms behind superconductivity and to find materials with even higher T_c values. This could lead to advancements in technologies such as magnetic levitation and quantum computing.