Primary dealers are a group of financial institutions that have an agreement with the Federal Reserve Bank to buy and sell government securities. These institutions typically include large commercial banks, investment banks, and other financial companies. They play a crucial role in the implementation of monetary policy by the Fed, as they can borrow money from the central bank through its discount window or by participating in open market operations. In return for their services, primary dealers receive certain benefits such as access to credit and information about the government's debt management program.