Short answers, pulled from the story.
The Bretton Woods system was the first fully negotiated international monetary order, established by the Bretton Woods Agreement signed on the 22nd of July 1944. Delegates from 44 Allied countries gathered at the Mount Washington Hotel in Bretton Woods, New Hampshire, to create a framework of fixed exchange rates anchored to the U.S. dollar, which was itself convertible to gold at $35 per ounce.
The Bretton Woods system collapsed because persistent U.S. balance of payments deficits, spending on the Vietnam War and domestic programs, and mounting inflation eroded confidence in the dollar's gold convertibility. On the 15th of August 1971, President Nixon unilaterally closed the gold window, ending the dollar's direct convertibility to gold. The system's formal end was ratified by the Jamaica Accords in 1976.
The Nixon Shock refers to President Nixon's decision on the 15th of August 1971 to close the gold window, making the dollar inconvertible to gold directly except on the open market. Nixon also imposed a 10% import surcharge and 90-day wage and price controls. The decision was made without consulting members of the international monetary system or even his own State Department.
Harry Dexter White was the chief international economist at the U.S. Treasury from 1942 to 1944 and drafted the U.S. blueprint for international monetary management that largely became the basis of the Bretton Woods system. He competed with John Maynard Keynes's rival British plan and favored a fixed pool of national currencies and gold over Keynes's proposed world reserve currency. President Truman initially named White as the first U.S. Executive Director of the IMF, but had to adjust his plans after FBI Director J. Edgar Hoover reported that White was linked to Soviet espionage.
Triffin's Dilemma was identified in 1960 by Belgian-American economist Robert Triffin, who observed that if the U.S. stopped running balance of payments deficits, the world would lose the liquidity needed to sustain economic growth, but if deficits continued indefinitely, confidence in the dollar as a reserve currency would eventually collapse. This structural contradiction proved fatal to the Bretton Woods system, as U.S. deficits grew through the 1960s and gold reserves fell from 55% to 22% coverage by 1970.
The Marshall Plan was a response to a dollar shortage that emerged because the U.S. was running large trade surpluses and European countries lacked the dollars needed to purchase American exports. From 1948 to 1954, the United States provided 16 Western European countries with $17 billion in grants, deliberately encouraging a dollar outflow to supply international liquidity. This outflow eventually became a dollar glut by the 1960s, which contributed to the erosion of the Bretton Woods system.