MT101
The SWIFT Request for Transfer, which a company sends to have a bank debit its account and pay someone.
Most MT messages travel between banks. MT101 is the exception that starts with the customer: a group treasury sends one or more payment orders and the bank executes them as ordinary transfers. The clever part is that the order can be forwarded. A company with accounts at ten banks in ten countries can send everything to its main bank, which relays the MT101 to wherever the account actually sits. That needs an agreement in advance, because otherwise the receiving bank sees a stranger asking to empty a customer's account.
Companies that don't want to join SWIFT send the same kind of order as files instead, in Europe often over EBICS. The ISO 20022 equivalent is pain.001, which is where most new development has already gone.