It's too early to gauge the political fallout from the Supreme Court's split decision Thursday to uphold President Obama's health-care law. But the ruling will have clear — and, in some cases, immediate — consequences for millions of Americans, from the uninsured to the poor to small business owners. Here, a brief guide to how the landmark 5-4 decision could affect you: 

Who will feel the biggest impact?
The "mammoth law" affects just about everybody, says Mark Trumbull at The Christian Science Monitor, but "the court's ruling has the biggest implications" for the roughly 50 million Americans who are uninsured. Many people have been unable to get coverage because of pre-existing conditions, and ObamaCare bars insurance companies from denying such consumers. Other Americans don't have insurance because they can't afford it. Under ObamaCare, the federal government will offer subsidies for those who need help obtaining coverage. For example, in 2014, a family of four making $60,000, with no employer-provided insurance, could get $9,308 toward their $14,245 in premiums. (Several online calculators can help you estimate what you might pay.)

What happens to people who refuse to buy coverage?
They'll have to pay a penalty — or, as the Supreme Court majority sees it, a tax. Although there are some exemptions, as a general rule, the penalty will be $285 per family or 1 percent of income, whichever is greater, starting in 2014. By 2016, the penalty will rise to $2,085 per family or 2.5 percent of income, whichever is greater.

Will poor people have to pay penalties, too?
Not necessarily. The law includes a provision that expands the Medicaid program, providing care for everyone under age 65 with income that doesn't exceed 133 percent of the federal poverty line (about $30,000 for a family of four). In theory, that would add 16 million Americans to the program. But thanks to the Supreme Court, there's a catch.

What's the catch?
The health-care law sought to force states to go along with the expansion by withholding federal Medicaid money to any state that refused to comply. But the court ruled that the federal government could only withhold new funding from those states, and not strip them of the Medicaid money they're getting already. This leaves open the possibility of states refusing to go along with the Medicaid expansion, potentially forcing many low-income Americans to obtain insurance on their own, or pay a fine.

What about people who already have insurance?
They'll be affected, too. A host of provisions affecting their coverage will remain in force. For example, children can stay on parents' plans until they're 26; insurers can't limit lifetime benefits; companies won't be able to deny new coverage due to pre-existing conditions; and insurance customers will be able to get preventive care with no out-of-pocket charges (including free birth control, provided you don't work for a faith-based organization that opposes it).

Anyone else?
Yes. Small-business owners with fewer than 25 employees and average annual wages under $50,000 will get tax credits for offering their employees coverage.

Sources: CBS News, Christian Science Monitor, CNN, Kaiser Family FoundationMother Jones, New York Times (2), Slate, Washington Post