Could you explain the Marshall Plan and Truman Doctrine? What is the difference?

The Truman Doctrine and Marshall Plan were two seperate parts of United States foreign policy during the Cold War. I like to think that the Marshall Plan was part of the Truman Doctrine. It's easiest to understand both things if we discuss the Truman Doctrine first.

The Truman Doctrine was the overally message that President Truman wanted to get across during his time as president. It was his most important piece of policy, around which all the rest of his foreign policy revolved. The basic idea of it was to hold back the growth of the Soviet Union (The USA's most prominent rival) which we call containment. So in a way, the terms "containment" and "The Truman Doctrine" mean the same thing, and are both important terms to remember for your America exam! 

Now we come to the Marshall Plan. This was an idea of General George Marshall, and involved giving lots of aid (money, food and other things) to European countries like France, Greece and West Germany, in the hope that this would stop them from turning to communism. It's useful to remember that the total amount donated was $17 billion. It's also important to remember that Stalin did not allow communist countries to accept this money. 

So the key points to remember are that the Truman Doctrine was an idea, and the Marshall Plan was America's way of putting that idea into practice.