Based on the interaction between superconducting macroscopic quantum effects and environmental electromagnetic field, superconducting detectors can provide ultrasensitive detection with quantum-limit sensitivity. Superconducting nanowire single-photon detectors (SNSPDs), with their outstanding features such as high detection efficiency and low dark count rate, have been widely applied in various fields including quantum information, deep space communication, and lidar. As the key detectors in the prototype optical quantum computer “Jiuzhang” and quantum key distribution systems, they also played a major role in bringing China to the forefront of quantum information research. In this paper, I introduce the basic mechanism of the SNSPD and discuss its key metrics, related cryogenics, applications, and frequently asked questions. A preview of future developments is also given.