With an Organization Access Token you can access our more advanced API's to access top-level information of your Mollie account. For example, you can retrieve all settlements and invoices of your account to automate your bookkeeping. For more details please read the authentication guide in our docs.
You can create an Organization Access Token easily in your Mollie Dashboard via Developers.
If you don't want to use the advance API's and only want to create payments or orders you can use the API-key instead.