A health insurance marketplace offered by various U.S. states under the ObamaCare law where people purchase insurance from competing insurance companies. The exchanges officially begin accepting enrollment on October 1, 2013 with coverage taking effect on January 1, 2014. The insurance plans offered by the exchanges are grouped into tiers, including bronze, silver, gold and platinum. The average cost for a typical silver plan is $328 per month, with the government subsidizing for those in need --those who earn 400% of the federal poverty level , $94,200 for a family of four, or $45,960 for a single person.