The Sorcerer's Stone—which was referred to as the Philosopher's Stone in the British edition of the film—is a legendary magical and alchemical item.

We'll let our favorite bookworm explain it more precisely:

HERMIONE: The Sorcerer's Stone is a legendary substance with astonishing powers. It will turn any metal into pure gold and produces the Elixir of Life, which will make the drinker immortal.

If your first thought about the Sorcerer's Stone is "Hey, I want one," well, you're not alone. Voldemort also wants to get his mitts on the precious pebble—and not because he wants infinite gold. Big V wants that immortality. He wants it bad.

And J.K. Rowling didn't just make this up—the Philosopher's Stone first showed up as a literary device around 300 AD, and has appeared in some form in myths and legends all over the world.

In the Middle Ages, people thought it actually existed, and since folks back in the Middle Ages also believed in witches and wizards enough to burn people at the stake (not cool, guys), it only made sense that Rowling would use it in her story about them.

On a more technical level, the Sorcerer's Stone is a MacGuffin: a device whose sole existence is to drive the plot forward. Voldemort wants it because it can restore the dead to life, but in truth it doesn't matter what it can do. It only matter that the bad guys want it and the good guys have to get to it first.

MacGuffins can be anything from the secret plans in a spy movie to the jewels in a heist movie, and more prominent examples have included the Maltese Falcon, the Ring of Power and anything Indiana Jones ever left his sitting room for. The Stone is all we need to know to set the story moving…which makes it important enough for J.K. Rowling to put the dang thing in the title.