For the second time, the Supreme Court of the United States has upheld the Affordable Care Act (ACA), President Obama's signature piece of legislation. And though this decision is being hailed as a political victory for the Obama administration, it is really a victory for millions of Americans who were saved from facing unaffordable health insurance costs.

In the case King v. Burwell, a key portion of the ACA, also known as Obamacare, was challenged: federal subsidies. Under the ACA, all Americans must purchase health insurance. For Americans who cannot afford health insurance (yet are also not poor enough to be on government-provided Medicaid), federal subsides bridge the gap and help them get health insurance.

Here's where it got tricky. In order to facilitate purchase of health insurance, the law also instructed states to create online marketplaces for citizens to purchase health insurance. For the 27 states who refused to create a marketplace -- or exchange -- the federal government created an exchange for them.

A poorly written part of the law, however, seemed to indicate that people buying insurance on the federal exchanges would not be eligible for federal subsidies. Without the subsidy, health insurance would have too expensive for more than six million people.

The court rejected that argument, and that's good news for these people: