1. The contract version means that you have signed a contract with Verizon or AT&T, two telecommunications companies in the United States

2. The contract must be signed for two years, and you can only use the contract within two years. If you use the services of that company, you will have to pay a fine if you break the contract. Not all Americans buy the contracted version. If you don't sign, you can change the telecommunications company, and the phone bill is cheaper if you don't sign.

3. The contracted version cannot be cracked in China. You can only use the card sticker to make calls. The non-signed version can be cracked

4. The signed version can use Verizon or AT&T's 3G network. Bare metal can only use wifi to access the Internet

This is all I can think of, there is only one hour left before the problem is over, sweat. . .

Hope this helps you