High-temperature superconductivity refers to superconductivity achieved at temperatures above 50 K, significantly higher than the traditional low-temperature superconductivity, which occurs at low double-digit Kelvin temperatures. The highest critical temperature recorded is still above 100 K, but this is still below room temperature. The classification of "high" temperature superconductors emerged after the discovery of cuprate superconductors in 1986, which challenged previous assumptions about temperature limits. These superconductors often possess a layered crystal structure and exhibit poor conductivity in their normal state, resembling ceramics. The term "high-temperature superconductor" can also apply to materials with lower critical temperatures if they share similar structural and superconducting mechanisms.