G-MSC stands for "Gateway Mobile Switching Center". It is a component in the Global System for Mobile Communications (GSM) network that provides call control and switching functions between the mobile network and the public switched telephone network (PSTN). The G-MSC acts as an interface between the mobile network and the PSTN, and it provides functions such as call routing, call setup and teardown, and call transfer. The G-MSC is responsible for routing incoming calls to the appropriate mobile subscriber and for routing outgoing calls from the mobile subscriber to the appropriate destination. It is a critical component of the GSM network and is essential for enabling mobile subscribers to make and receive calls to and from the PSTN.