Mobile station consist of two parts i.e. handset and a Subscriber Identity Module (SIM).
SIM stores integrated circuit card identifier (ICCID), International mobile subscriber identity (IMSI) and Authentication key (Ki -128bit) which is used to identify and authenticate subscriber in network. Refer further details on SIM card here.
The range and coverage area of a mobile station depend on the output power of mobile.
States of a mobile station: Idle (mobile is ON but no call), Active (call on progress) and Detached (mobile switched off).