What are the Federalist Papers and why are they important to the issue of the second Amendment?

The Federalist Papers are a series of 85 essays published in late 1777 and early 1778 by John Jay, James Madison and Alexander Hamilton, all using the pseudonym Publius, explaining, expounding and seeking to persuade New York to ratify, the Constitution. To my knowledge they have nothing whatsoever to do with the 2nd amendment because that was written by the first congress, after ratification, in 1789.

Additional Information:

The 2nd amendment has a infamous words "A well regulated Militia" which many of the left wing gun control activist interpret to mean the military or national guard, the federalist papers explain what the found fathers, authors of the 2nd amendment, considered a "Militia" that being "all able bodied men" not a government power or agency. The Concerns layout out in the Federalist papers show that the 2nd amendment was including as the last line of defense against a over powered central government, ensuring the freedom of the people was never taken away.

So the federalist papers do play a fairly big role in understanding the 2nd amendment