Q: what is the simm card used for?

wdbsami wrote:

 

I don't know what the sim card is for?

To activate your phone and for cellular data from your cell phone provider.

From iPhone: Understanding SIM cards - Apple Support

Just like most cellular phones, the iPhone uses a SIM card to determine the phone number, carrier, and features are available for the account. However, the iPhone does not store contacts and phone numbers on the SIM card.

The SIM card is needed by your cellular provider to identify the phone on their network. Without that, the phone can't connect with your carrier. That makes it an expensive iPod.  The SIM card requires no user interaction as long as it remains where it is.  It is used by your carrier only.

wdbsami wrote:

 

I don't know what the sim card is for?

Using google you can find this: http://en.wikipedia.org/wiki/Subscriber_identity_module