Request to Pay
A standardised message in which the payee asks for money and the payer taps approve, kicking off a transfer from the right account for the right amount.
The message itself moves nothing. It is a digital bill that lands in the payer's banking app with amount, payee and reference already filled in, and the payer can accept, decline or postpone it. Acceptance triggers an ordinary credit transfer, in Europe ideally over SEPA Instant. Unlike direct debit there is no mandate: the payer pushes the money and stays in control.
The European Payments Council published the SEPA Request-to-Pay rulebook in November 2020, with messages built on ISO 20022 (pain.013 and pain.014). The UK has its own flavour from Pay.UK. Anyone who has received a payment request in Swish knows the idea. As usual, the hard part isn't the technology, it's getting thousands of banks onto the same scheme.