From the article above:
The 2010 law, the Affordable Care Act, requires non-exempted individuals to maintain a minimum level of health insurance or pay a tax penalty.
The essence of Roberts’s ruling was:
• “The Affordable Care Act is constitutional in part and unconstitutional in part,” Roberts wrote.
• “The individual mandate cannot be upheld as an exercise of Congress’s power under the Commerce Clause. That Clause authorizes Congress to regulate interstate commerce, not to order individuals to engage in it.”
• But “it is reasonable to construe what Congress has done as increasing taxes on those who have a certain amount of income, but (who) choose to go without health insurance. Such legislation is within Congress’s power to tax.”