Short answers, pulled from the story.
Cash and Carry was a United States policy announced by President Franklin Delano Roosevelt on the 21st of September 1939. It allowed belligerent nations to purchase war materials from the US provided they paid immediately in cash and transported the goods on their own ships. It replaced earlier neutrality laws that had banned arms sales entirely.
Roosevelt designed the original cash-and-carry clause in the Neutrality Act of 1937 as a deliberate way to assist Great Britain and France in any war against the Axis Powers. He calculated that only Britain and France had both the hard currency and the ships needed to use the arrangement, making the nominally neutral policy functionally favorable to the Allies.
The Neutrality Act of 1939, passed by the House on the 2nd of November by a vote of 243 to 181 and signed by Roosevelt on the 4th of November, lifted the ban on selling military arms to belligerents. It kept in place prohibitions on American loans to warring nations and on the use of American ships for transport.
Isolationists in the Senate and House feared that allowing arms sales would draw the United States into the conflicts in Europe and Asia. The bill was defeated repeatedly until Germany's invasion of Poland in September 1939 shifted congressional opinion, with Senator George W. Norris arguing that failing to repeal the embargo would effectively help Hitler.
The Nye Committee concluded that United States involvement in World War I had been driven by the private interests of arms manufacturers. That finding convinced many Americans that investment in a belligerent nation would inevitably lead to US participation in war, and it shaped the isolationist sentiment behind the neutrality acts that Cash and Carry eventually replaced.
Cash and Carry ended the arms embargo in place since 1936 and allowed Allied nations, particularly the United Kingdom, to buy military equipment from the US. Because it required immediate cash payment, it had a built-in limit as Allied resources came under strain. Roosevelt's Lend-Lease program was the direct successor, removing the cash requirement that Cash and Carry had imposed.