Sending and receiving digital currencies

Hello everyone I have a puzzling question. Someone requested a USDT receiving address, and I sent it to them. When they sent it, I checked the contract and found that it was a separate, different contract on the USDT. This is confusing. I want to know how they did that. Digital currencies are supposed to be secure; how did this happen?

If the USDT appears under a different contract, it doesn’t necessarily mean the security of digital currencies has been compromised. In many cases, the sender may have used a different blockchain, a bridged version of USDT, or a token that shares the same name but has a different contract address.