Source: Board of Governors of the Federal Reserve System (US)  

Release: H.6 Money Stock Measures  

Units:  Billions of Dollars, Not Seasonally Adjusted

Frequency:  Monthly

Notes:

The Board of Governors consolidated this series onto the Statistical Release H.6, "Money Stock Measures", after the H.3 statistical release was discontinued. For more information on the consolidated H.6 release, see the H.6 Technical Q&As.

This series is a sum of total reserve balances maintained plus vault cash used to satisfy required reserves.

Source: Federal Reserve Bank of New York  

Release: Temporary Open Market Operations  

Units:  Billions of US Dollars, Not Seasonally Adjusted

Frequency:  Daily

Notes:

This series is constructed as the aggregated daily amount value of the RRP transactions reported by the New York Fed as part of the Temporary Open Market Operations.

Temporary open market operations involve short-term repurchase and reverse repurchase agreements that are designed to temporarily add or drain reserves available to the banking system and influence day-to-day trading in the federal funds market.

A reverse repurchase agreement (known as reverse repo or RRP) is a transaction in which the New York Fed under the authorization and direction of the Federal Open Market Committee sells a security to an eligible counterparty with an agreement to repurchase that same security at a specified price at a specific time in the future. For these transactions, eligible securities are U.S. Treasury instruments, federal agency debt and the mortgage-backed securities issued or fully guaranteed by federal agencies.
For more information, see https://www.newyorkfed.org/markets/rrp_faq.html