Oh no problem! I understand a lot of people don't know this! I only know this from my comp/phone wiz husband and my last call center job for dtv. They have cards that are similar for their tv boxes/receivers!
A sim card is how some companies distribute their system services. Some phones have it built in and others have a card with the system on it. The only difference is one you don't need to and the other you have to insert the card where the battery is. There will be a slot for it