What is the Affordable Care Act (ACA)?

What is the Affordable Care Act (ACA)? What are the Supreme Court cases that have defined, explained, and expanded the Act? What is the current Congress doing with respect to appealing, replacing, or refining the Act? Should the ACA be repealed, revised, or stay the same? What changes, amendments, or modifications would you make to the current law and why? What about changes to the regulations?