How were the Truman Doctrine and Marshall Plan similar and how were they different?

Both the Truman Doctrine and the Marshall Plan were part of the United States' policy of containment during the Cold War. "Containment" referred to the United State's strategies to prevent the spread of Communism. The containment policy had military, economic, and diplomatic aspects.

The Truman Doctrine made containment the United State's official policy in March 1947, when Truman's pledged to "support free peoples who are resisting attempted subjugation by armed minorities or by outside pressures." The Truman Doctrine was a statement of the United States' policy of supporting capitalism and fighting communism during the Cold War. It was applied to the conflicts in Greece and Turkey during Truman's presidency. The spread of communism was prevented in these two countries. 

The Marshall Plan was an economic plan for the recovery of Europe. The United States would give significant funds to countries in Europe recovering from World War II. It was part of the United States' containment policy in that it was meant to prevent the spread of communism in European countries by helping Europe prosper. George Marshall, U.S. Secretary of State at that time, believed that communism is more likely to spread to countries that are struggling economically. The Soviet Union and its allies refused to receive aid from the Marshall Plan. Thus, the Marshall Plan was representative of another standoff between the "free world" and communist countries.

The difference between the Marshall Plan and the Truman Doctrine is that the Marshall Plan was a systematic plan for providing European countries with economic aid, while the Truman Doctrine was a more general statement of United States policy toward communism.