The Supreme Court will begin hearing arguments on a case related to the Affordable Care Act today. The case centers around the constitutionality of the individual mandate and whether the mandate is severable from the ACA more broadly (i.e. whether the mandate can be struck down without removing the legislation entirely). The lawsuit is the third ACA-related case to reach the Supreme Court since the legislation was passed in 2010, and a decision on the case is not expected until next year.
More context: A coalition of 18 states (led by Texas and supported by the Trump administration) is arguing that the individual mandate is unconstitutional and that the entire ACA must therefore be struck down. The lawsuit is being challenged by a coalition of 21 states (led by California), who are seeking to leave the ACA in place.
Extra: The Affordable Care Act, commonly referred to as “Obamacare,” was passed in 2010 (wiki).