When you authorize third parties and their respective service providers to collect your financial data, it's referred to as "account aggregation" or "linked external accounts". These terms are interchangeable and mean the same thing. 

When you enroll in their service, you're redirected to a U.S. Bank login screen to enter your username and password.
By authenticating your identity with us (U.S. Bank), it allows you to share your information without disclosing your login credentials to the third party.