While there's far more to the Affordable Care Act (the ACA) than we can fit into a simple article, Team Randi has boiled down what the Supreme Court fight is about, with some help from sources like Sarah Kliff at the Washington Post.
To start with, the Supreme Court won't be deciding whether the entire Affordable Care Act is legal - just four parts of it.
PART I: The Anti-Injunction Act
There is a U.S. law, dating from 1867 that says that the government can't be dragged into court over a tax until someone is actually forced to pay the tax. If the penaties for those who choose not to purchase insurance are not considered a tax, the Anti-Injunction law may not apply to the ACA. However, if SCOTUS decides the penalties are a tax, since the penalties in the ACA don't start until 2015, there may be no one legally allowed to sue over this issue until 2015 - after the ACA has been implemented.
PART II: The Individual Mandate
You've probably heard the most about this part of the ACA. This is part of the law that says that - in order to promote the general welfare of Americans, by helping to provide a health care system that all Americans can afford - all Americans must have health care insurance, or otherwise pay a penalty. This is also the part of the ACA that forces insurers to cover ALL Americans, regardless of pre-existing conditions.
PART III: Severability
This third argument is trying to answer this question: Can The Court say that the individual mandate is unconstitutional, even if the rest of the ACA remains constitutional and legal? According to an earlier ruling by the Eleventh Circuit Court, the Court could do just that. If SCOTUS did that, however, they could plunge the entire health insurance industry into ruin - because insurance carriers would still be forced to cover everyone, while healthy people would no longer be forced to join the insurance pool.
PART IV: Medicaid Expansion
This is the part of the law that expands Medicaid to cover significantly more poor Americans, while increasing the amount that states have to pay. Since Medicaid is a federal and state partnership program, this part of the law also forces states to carry more of the burden, instead of dumping most of the cost on the federal government.
If you're looking for even more information on the Supreme Court and the ACA, feel free to click on some of the related links, below.
Frequently Asked Questions: The Supreme Court and health reform
A Technicality That Might Save Obamacare: The Anti-Injunction Act
Hostility to health law's individual mandate is foolish
Analysis: Why Supreme Court may uphold healthcare law
Individual mandate clearly constitutional
Why the Individual Mandate Is Effective and Efficient
David Plouffe: Mitt Romney ‘Godfather’ of the Individual Mandate
What happens if the individual mandate falls, in one chart
The Severability Doctrine
Medicaid Expansion Is a Key Part of Affordable Care Act
How the Roberts court could save health care