US iTunes card is a way to reload iTunes credits to your US iTunes store or App store account so that later you can purchase movies, music, apps, books, TV shows and many more things. Please note Apple will have different iTunes card for each country (or each iTunes store). So these US iTunes cards can only be used on US iTunes store. Don't worry if you do not have a US iTunes store account yet, it is very easy to open a new account. If you get can into any troubles, we definitely can help.
One common question is that I can use US iTunes card from outside US. The answer is YES as long as you have a US iTunes account. Your physical location where you access your iTunes account is not a concern for Apple / iTunes store. At this moment, you do NOT have to use any VPN or DNS service to use US iTunes store. That will make things easier for people in military, people travelling or simply people living outside US that want to access some exclusive content of the US store.