SIM

data/Digital Identity card used in a GSM Cell Phone

The equivalent of SIM on CDMA networks is the R-UIM (and the equivalent of USIM is CSIM). http://en.wikipedia.org/wiki/Subscriber_identity_module

Under some conditions some Address Book data, and some SMS messages, are stored in the SIM. But this isn't a big factor in Smart Phone-s (so you don't have to worry about not having your contacts available when you swap SIM cards for international roaming - 2011-06-01-SimpleCheapInternationalRoaming). http://en.wikipedia.org/wiki/Subscriber_identity_module#SMS_messages_and_contacts