In one of the most historic decisions made in American health care, the U.S. Supreme Court upheld the health care reform law in a 5-to-4 decision.

“This ensures that as of January 2014, for the first time, tens of millions of Americans will have access to affordable health care,” said Dr. Jonathan Jaffery, a nephrologist and health care policy expert at the University of Wisconsin.

Perhaps the most hotly contended question was how the court would rule on the so-called “individual mandate,” which requires people to buy health insurance or pay a penalty.

According to Chief Justice John G. Roberts, the mandate was upheld because, for people who decide not to purchase a health coverage plan, the penalty constitutes a tax, which means it is within Congress’ power to enact it. “Since Congress is allowed to tax, then it’s constitutional,” Jaffery explained.

But the court did find fault with the law’s provision to expand Medicaid, stating that the federal government couldn’t force states to accept the expansion by withholding Medicaid funds from states that chose not to participate.

The law would expand Medicaid coverage to include everyone with an income less than 133 percent of the poverty level. [Vote in our Poll: Do you like the ruling on health care reform?]

The number of Americans without health coverage rose from 49 million in 2009 to nearly 50 million in 2010, while the number of insured Americans rose from 255 million to 256 million, according to the U.S. Census Bureau.

Because of the ruling, most provisions of the law that are slated to take effect in 2014 will go forward. Here are seven facts you should know about the health reform law.

1. You can’t be denied coverage if you have a pre-existing condition

Already in effect, this part of the law protects people who suffer from an illness or disability. People who apply for health insurance coverage can’t be denied for these reasons. Insurance companies also can’t deny coverage to children who have pre-existing conditions.

2. Parents can continue to pay for their children’s insurance

Also already in effect, this portion of the law allows young adults to stay on their parent’s insurance plans until age 26.

3. Depending on which state you live in, you may be eligible for Medicaid

The court’s ruling announced today means that states can choose whether they will participate in the expansion of Medicaid. It’s likely that a number of states will go along with the law’s provision to provide coverage to people with incomes less than133 percent of the federal poverty level, Jaffery said.

“For those states that opt-out of expanding their Medicaid programs, this will mean that many people will continue to have limited access to health care,” Jaffery said.

4. No annual or lifetime dollar limits

Under the law, lifetime and annual dollar limits for all insurance policies will be phased out by 2014. In other words, insurance companies can’t place dollar limits on the coverage people receive each year or over a lifetime.

5. Insurance premiums must remain affordable

With the individual mandate in place, people can receive health care coverage regardless of whether they are sick or healthy. But the law requires that insurance companies keep monthly premiums within an affordable range for everyone.

“This allows insurance companies to provide affordable care without going out of business,” Jaffery said.

6. For people without insurance coverage, there’s help

In January 2014, Americans will be required to buy health insurance.

Each state will set up a “market exchange,” allowing those who are uninsured or underinsured to shop for a health care plan that they find affordable.

“Depending on your income level, you’ll receive subsidies [financial help] to help you purchase a plan,” Jaffery said.

7.   If you don’t buy health insurance, there’s a penalty

If you decide to not buy coverage, the penalty could start at $95 a year, or up to 1 percent of your income, and continue to increase to 2.5 percent by 2016, according to the Kaiser Family Foundation.

But people who still can’t afford a monthly premium because of their income, suffer from financial hardship, or have religious objections to the law will not have to purchase a plan, nor will they they required to pay the tax penalty for not doing so.

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