User's Manual

page 35
It includes international and domestic roaming. In this manual it refers
to international roaming only.
STK The full name is SIM ToolKit,a new service of GSM.It can provide
you with smart information functions,such as stock information,traffic
information,weather forecast,etc.The provided functions of STK
depend on your network provider.The service needs support of both
the SIM card and the network.