Anti-Injunction Act
What it is: The Court opens its oral arguments with a debate over whether it can even issue a ruling on the Affordable Care Act since its penalties for not carrying insurance have not come into effect yet. Under a law passed in 1867, the Anti-Injunction Act, a tax cannot be challenged until someone has actually had to pay it. Health reform’s penalties don’t start until 2015.
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The individual mandate
What it is: The most-contested part of the health reform law, the Affordable Care Act’s individual mandate requires nearly all Americans to carry health insurance. The legal question centers on whether such a regulation is permissible under the Commerce Clause, which allows the federal government to regulate interstate activity.
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Severability
What it is: The question of whether the health reform law can stand without the individual mandate — in legal parlance, whether the individual mandate is “severable” — is a pretty crucial one. The Supreme Court will hear arguments on if it could strike down that part of the law, while letting the rest of it stand.
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Medicaid Expansion
What it is: The health reform law expands Medicaid to cover everyone under 133 percent of the federal poverty line (about $14,000 for an individual) in 2014. Medicaid is run as a state-federal partnership and, right now, states are only required to cover specific demographics, groups like low-income, pregnant women and the blind or disabled.
http://www.washingtonpost.com/blogs/ezra-klein/post/wonkbook-absolutely-everything-you-need-to-know-about-health-reform-supreme-court-debut/2012/03/26/gIQAb7adbS_blog.htmlThe Reuters article has been updated since the OP was made; it's now titled 'Supreme court unlikely to delay Obama healthcare ruling', and says the justices seem to agree that the rest of the cases can be heard now (unsurprising, since the government and the plaintiffs agree on that too). So that looks like the first part out of the way.
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