A state marketplace is similar to the larger health insurance marketplace run by the federal government. The main difference being the individual market is maintained by the state. In general, state marketplaces and their plans are required to adhere to the same ACA regulations that apply to the federal marketplace.
Why do some states have their own marketplace?
The option for states to have their own health insurance marketplaces was presented with the passing of the Affordable Care Act (ACA).
State marketplaces now generally fall into two categories. Some states like Massachusetts launched marketplaces prior to the ACA and were allowed to keep using it once the ACA passed. Other states like Pennsylvania chose to make their own marketplace after the ACA was passed and were granted a waiver– sometimes this is due to cost (the federal platform charges states a fee) and other times it's just political. Currently, 14 states, along with Washington DC, have state marketplaces: