A state marketplace is similar to the federal health insurance marketplace, except the marketplace is maintained by the state itself rather than the federal government.
Just like on the federal Marketplace, and all the plans you'll find through Catch, all plans are held to rigorous ACA-compliance standards. That means they cover essential health benefits like preventive care, and are available even to folks with pre-existing conditions.
Nineteen states, plus Washington DC, have state marketplaces: