People can pay you by tapping your phone if your phone is compatible.
Apple iPhone's can be used to have a customer or someone use their tap to pay debit card or credit card to make a payment to you and pay you.
You can see how the tap to pay with card works on your iPhone at the link below.
https://www.apple.com/business/tap-to-pay-on-iphone/
Not all phones are compatible and not all phones can be used to allow someone to use their debit card to make payments to you but sometimes works on some phones.
If you have an iPhone or Apple Watch and the other user has an iPhone or apple watch they can use their phone to pay you using Apple Tap to Cash to send payments to you or you can also make payments to them.
When the money is transferred, it's private and your email and phone number are not shared.
To make a payment using Tap to cash.
Open the Wallet app, tap your Apple Cash card, then tap Send or Request.
Select Tap to Cash.
Enter the amount, then add a note if you want to identify what the payment is for. Tap Next.
Double-click the side button to confirm.
Hold the top of your iPhone near another iPhone or Apple Watch.
If using an Apple Watch to send the payment.
Open the Wallet app, tap your Apple Cash card, then scroll down and select Tap to Cash.
Enter the amount you want to send, then tap Continue.
Double-click the side button to confirm, or tap Apple Cash to change your payment method.
Hold your Apple Watch near another Apple Watch or iPhone.
You can send or receive a maximum of $2,000.00
As for someone tapping your phone to get payment they cannot simply just tap your phone and get money without your authorization as you have to authorize payment.
There are prank videos on YouTube of someone using their phone to tap another persons phone and take money but in reality that cannot be done.
If someone comes up to you with a phone and taps your phone and you did not authorize it, the money is safe.