Banks must, if the customer so wishes and agrees, give authorised third parties access to the customer’s account information and transaction history. These can be both competing banks and other institutions. These service providers will also be able to initiate payments on behalf of customers directly from the customer's account.
When we buy something online we typically enter our payment details into the merchants website, and the merchant then gets the money from your bank account by way of a few intermediaries:
* With PSD2, the Directive will allow retailers to ‘ask’ consumers for permission to use your bank details. Once you give permission, the retailer will receive the payment directly from your bank – no intermediaries
* The direct connection between retailers and banks will be enabled using Application Programming Interface or APIs for short
* The use of API’s is exciting because it enables companies (innovative companies) to connect to financial institutions directly
See also https://www.starlingbank.com/blog/explaining-psd2-without-tlas-tough/