Kathryn Johnson at her Capitola home Saturday, Sept. 21, 2013. She pays a large health care premium every month. On the eve of the Oct. 1 kickoff when Americans can start shopping for insurance under the U.S. Affordable Care Act, many Bay Area residents still aren't sure what it means to them, or how the state's healthcare exchange and subsidies work. (Patrick Tehan/Bay Area News Group)