From Investopedia
What is Account Aggregation?
How Account Aggregation Works
Account aggregation usually occurs only within a single financial institution. However, certain assets held outside a financial institution may be included if the account holder has agreed to that.
Many personal finance services offer customers the ability to aggregate data from all of their savings, checking, and brokerage accounts, as well as other financial assets across all the institutions with which they do business. These services usually require that users provide account-access information, such as a username and password, for each of the accounts that they wish to include in the aggregation. Using this information, the service "scrapes" or downloads account balances and other data from each account to include in the aggregation.
However, account aggregation software is often allowed only to access balance information and transaction records. And for security reasons, many aggregation services do not permit users to make transactions from within the service.
In addition to aggregating data from savings, checking, brokerage, and other financial accounts, some aggregation services and software—particularly those used by professional financial advisers on behalf of their clients—aggregate additional net-worth data, such as recent home-value estimates. Account aggregation platforms may also categorize cash inflows and outflows.
From "The Balance"
Account aggregation services only give the software permission to view your account balances and transactions, not make transactions. If you actually want to access your money or move it, you would need to sign in to each account's website.
Additionally, the software draws on many advanced security features. For example, if you are logging on from an unknown computer or device, additional authentication will likely be necessary.

The Federal Reserve has raised interest rates to their highest level since early 2008. Yet the biggest commercial banks are still paying peanuts to savers. In theory, savers could have earned $42 billion more in interest in the third quarter if they moved their money out of the five largest U.S. banks by deposits to the five highest-yield savings accounts—none of which are offered by the big banks—according to a Wall Street Journal analysis of S&P Global Market Intelligence data.
The five banks—Bank of America Corp., Citigroup Inc., JPMorgan Chase & Co., U.S. Bancorp and Wells Fargo & Co.—paid an average of 0.4% interest on consumer deposits in savings and money-market accounts during the quarter, according to S&P Global. The five highest-yielding savings accounts paid an average of 2.14% during the same period, according to data from Bankrate.com. These five banks collectively hold about half of all the money kept at U.S. commercial banks in savings and money-market accounts tracked by the Federal Deposit Insurance Corp. That share has held steady despite the availability of higher rates elsewhere.
The $42 billion gap in the third quarter was the largest amount since record-keeping began, but will likely be dwarfed in the fourth quarter because top high-yield savings accounts have raised their interest rates to more than 3.5%.
Since the start of 2019, Americans have lost out on at least $291 billion in interest by keeping their savings in the five biggest banks. That total balloons to $603 billion when going back to 2014, when the FDIC started tracking consumer deposits in money-market and other savings accounts.
And U.S. savers have likely missed out on much more than $600 billion because the average rate the five biggest banks have paid over the past eight years, 0.24%, includes higher-yielding money-market accounts and some business accounts. Traditional savings accounts paid an average rate of 0.02% at the five largest banks during that period.
Why haven’t savers moved more of their money? Some customers aren’t aware of how much money they could make by switching, and others just don’t care. Alicia Gillum has been with Bank of America for 26 years and says she has no interest in searching for a new bank, even though her savings of more than $100,000 is earning almost no interest. Her loyalty has earned her Platinum Honors Tier status, which affords her a 0.04% interest rate on her savings instead of the 0.01% rate the bank pays to customers of its basic savings accounts.
Americans flush with stimulus payments and enhanced unemployment checks flooded U.S. banks with deposits earlier in the pandemic. The biggest banks got an outsize share of those deposits. About $425 billion flowed into money-market and savings accounts at U.S. commercial banks between the first quarter of 2020 and the third quarter of 2022, according to the FDIC. More than 95% of that went to the five largest banks.
But things could be changing. The average rate on money-market and savings accounts at the five largest banks nearly tripled in the third quarter from where it was in the second. And people are starting to move their money around in other ways to take advantage of higher rates, pouring a record amount into higher-yielding savings vehicles such as Series I savings bonds and Treasury bills this year.