GSM is a digital cellular network standard that was developed in 1982. It has a three-layer architecture consisting of the mobile station, the base station subsystem, and the network switching subsystem. GSM provides telecommunication services as well as data services and supplementary services. Some advantages of GSM include better speech quality, support for data transmission, and international roaming. However, GSM also has some disadvantages such as potential security issues and less efficient use of spectrum compared to newer technologies.