Hi John,
A bank transfer is when you send money directly from your bank to another bank account. You need to make sure you know and trust the person you’re transferring the money to – unlike things like cheque fraud, it’s much harder to reclaim losses from fraudulent transfers.
If someone you don’t know is asking for a bank transfer, do serious research! If you think it’s legitimate, but don’t want to transfer, find out if there’s another way to pay them – for example, on a credit card, which offers you more protection.