Financial Institutions put collateral into an overnight market and receive cash, and then they "agree" to "repurchase" / give the cash back (plus some fee) for the collateral the next day - right?
This is the "opposite" in that Financial Institutions put cash in and get collateral (treasuries) out - right? The transaction is essentially going in the "reverse" direction it traditionally went - which is why it's the "reverse repo market".
It's interesting because "having too much cash" is not usually a problem. Now it is.