Basically Law

The Second Amendment reads:

A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.

The language of the Second Amendment has been the subject of controversy.  Does the Amendment create an individual right to bear Arms or a collective right?  In Heller, the Supreme Court finally decided it is an individual right and that is the correct decision.

A collective right makes no sense.  Does a collective right mean that I cannot personally carry a gun, but if I get five persons and form a "collective group" then we can all carry guns.  That cannot be right.  The other way people view it as a collective right is that it applies to the right of the States to form Militias, but that cannot be right either.  It would be strange that of the first eight amendments to the Constitution, only one protects a State right while all the others protect individual rights.  Also, what in the Constitution would prevent States from creating Militias without this Amendment?  Nothing.

Therefore, it has to be an individual right and history backs it up.  I take an interesting read on the Amendment.  The first section of the sentence, "A well regulated Militia, being necessary for the security of a free State," does not involve any rights but just sets up and explains why "the right of the people to keep and bear Arms, shall not be infringed."  The colonists feared standing armies since they can be used as a tool of oppression, but such armies are needed to protect the country from a foreign invasion (or internal insurrection).  In order to counter the possible oppressive use of a standing army or Militia, the people need to have guns themselves to keep the standing army in check.

Allowing individuals to carry guns protects them from having the State from oppressing their freedom.  That is what the Second Amendment is there to prevent and to protect.