This command has to do with Cisco’s wireless infrastructure. Specifically, it has to do with the Cisco Mobility Services Engine (MSE), which is a Cisco product that provides advanced services for wireless networks including: location services, Wi-Fi client tracking, analytics services, and many other advanced features. You can find out more about MSE here.
Now MSE is essentially a server that connects to a Cisco wireless controller, and the Network Mobility Services Protocol (NMSP) is a Cisco protocol that is used for communication between the controller and the MSE server.
Now the command that you mention essentially tells the switch not to send any location and attachment notifications to a Cisco MSE. Attachment and location information includes elements such as RFID tags, rogue clients and access points, RSSI information, location information, and other contextual information such as state of device, presence information, telemetry data, and historical information. So any access point connected to such a port will not be able to send any of this information about clients connected to it via this port.
These commands pertain to wireless networks, and is probably in the CCNP or CCIE Wireless certification level.
I hope this has been helpful!