IPhone 5 enquiry, all help gratefully received!
Rather than provide a link offsite, the short answer is yes.

Turn off find my iPhone and then go to settings > general > reset and tap the one that erases all content and settings. You will then (after a reboot) have an (effectively) factory fresh iPhone suitable for selling to a stranger or giving to a small child.

The SIM is not affected, and it will retain it's phone number and wireless plan if any.