Who wouldn't know!? But for those who don't: Take off the back panel to your cell phone, then remove the battery, You should be able to see the sim card once you remove the battery.
Yes. Verizon phones on the home CDMA network wil work without the SIM card installed. I have a Blackberry Storm, fully functional without the SIM in it. Phones on other networks may have limited...
SIM cards securely store information and data which identifies the service provider. So with these information, your phone would use the services offered by the service provider.