You may want to read previous answers to similar questions in this sub to get more background, such as this response by /u/Georgy_K_Zhukov, and this response by /u/uncovered-history, and all the other posts on the topic in this sub's FAQ.

I'll just add to those previous responses that, in the academic community, the original purpose of the amendment is debated. There are two major schools of thought on the issue: the "individualist" view of the amendment and the "collectivist" view.

The individualists argue that the 2nd Amendment was intended to protect the individual's right to own firearms for some combination of purposes such as the protection of personal liberty, national defense, self-defense, defense against a despotic government, the protection of the right of revolution as well as to protect against unpopular revolutions/rebellions, and/or the right of the individual to provide for their family (i.e., hunting for food).

The collectivists argue that the 2nd Amendment was intended to protect the rights of the states against the federal government. The states had a right to form state-run militias and the amendment prevented the federal government's power to form national armed forces from going unchecked. It prevented the feds from using military force against the states without the states having the constitutional power to defend themselves in kind, i.e., militarily. Thus, the 2nd Amendment was intended to allow the states to regulate individuals' rights to own firearms, or to disallow them from owning them at all if they so wanted, because it allowed each state to determine how best to form a "well-regulated militia" of armed and trained citizens. The states even have the right to forgo such a defense altogether if they want.

Some academics take arguments from both schools of thought, and there is also overlap between the two schools. For example, the collectivists view the right as being one to protect against rebellions, to provide for national defense, and to defend against a despotic government, just like the individualists view it. But unlike the individualists, the collectivists argue that this was always intended to be a right exercised by state governments in their capacity to protect their state citizens as a whole, and was not intended to be exercised by individual citizens themselves.

At the Supreme Court level, the court has issued various decisions over the years supporting both views, though the court has rarely (ever?) explicitly rejected one view in its support of the other. In the 1939 decision United States v. Miller, the court appeared to support the collectivist view:

"In the absence of any evidence tending to show that possession or use of a "shotgun having a barrel of less than eighteen inches in length" at this time has some reasonable relationship to the preservation or efficiency of a well regulated militia, we cannot say that the Second Amendment guarantees the right to keep and bear such an instrument. Certainly it is not within judicial notice that this weapon is any part of the ordinary military equipment, or that its use could contribute to the common defense."

Similarly, the majority decision in the 1875 case of United States v. Cruikshank stated that the 2nd Amendment "has no other effect than to restrict the powers of the national government" which may be read as a rejection of the individualist view.

However, more recently, in the 2008 decision District of Columbia v. Heller, the majority opinion supported the individualist view:

"The Second Amendment guarantees an individual right to possess a firearm unconnected with service in a militia, and to use that arm for traditionally lawful purposes, such as self-defense within the home."

That isn't to say that the court hasn't put some limits on an individualist view. The Heller decision explicitly said that the 2nd Amendment is not unlimited, and that the government did have the ability to prevent citizens from possessing "dangerous and unusual weapons", though it didn't really go into any detail of what such a weapon would be. The court has also upheld the right of states to outlaw convicted felons from owning firearms.

For what it's worth, both the Cruikshank and Heller decisions were 5-4 decisions. The Miller decision was 8-0, but its holding is more ambiguous, since both sides of the argument have used it as evidence for their interpretation of the 2nd Amendment. Similarly, the 1886 case Illinois v. Presser was a unanimous decision that collectivist proponents have cited as supporting their interpretation, though individualists have refuted such a reading. The actual holding in the case stated: "Unless restrained by their own constitutions, state legislatures may enact statutes to control and regulate all organizations, drilling, and parading of military bodies and associations except those which are authorized by the militia laws of the United States."

The above is largely taken from The Bill of Rights and the States: The Colonial and Revolutionary Origins of American Liberties ed. by Patrick T. Conley, which includes a bibliography of sources for each of the two schools of thought.

You may also want to read (though be warned that many authors have a bias in promoting one view or the other, so it's important to get a cross section of academic views):

• "The Ideological Origins of the Second Amendment" by Robert E. Shalhope, published in The Journal of American History

• The Philosophy of Freedom: Ideological Origins of the Bill of Rights by Samuel B. Rudolph

• Origins of the Bill of Rights by Leonard Williams Levy

• A Well-Regulated Militia: The Founding Fathers and the Origins of Gun Control in America by Saul Cornell (this book promotes the collectivist argument -- consult the link to this sub's FAQ, as this book has specifically been asked about in this sub before)

• The Founders' Second Amendment: Origins of the Right to Bear Arms by Stephen P. Halbrook (this book is very much an individualist argument -- Conley's bibliography calls Halbrook "the most prolific individualist")

For reading on SCOTUS decisions on the the amendment, you may want to check out:

• "The Second Amendment: Structure, History, and Constitutional Change" by David Yassky, published in the Michigan Law Review

• "The Inconvenient Militia Clause of the Second Amendment: Why the Supreme Court Declines to Resolve the Debate Over the Right to Bear Arms" by Robert Hardaway, published in the Journal of Civil Rights and Economic Development

• "The Second Amendment and the Personal Right to Arms" by William van Alstyne, published in the Duke Law Journal

You may also want to directly read the sources cited in Conley's bibliography linked above. And both of the previous responses in this sub--by Georgy_K_Zhukov and uncovered-history--linked above have many more sources worth reading as well and should also be consulted (for uncovered-history's sources, you'll have to scroll down the thread a bit to find them).

EDIT: I realized that my Google Books link to Conley's bibliography only shows the first page. Here again is a link to that first page, which includes the individualist sources. And here is a link to the second page, which includes the collectivist sources.