Minimum essential coverage is the category of health coverage that satisfies the Affordable Care Act's individual coverage requirement. Section 5000A of the Internal Revenue Code still provides that an applicable individual "shall for each month beginning after 2013 ensure that the individual, and any dependent of the individual who is an applicable individual, is covered under minimum essential coverage for such month," and section 5000A(f)(1) lists what qualifies. HealthCare.gov describes it as "Any insurance plan that meets the Affordable Care Act requirement for having health coverage," noting that it is "sometimes called 'qualifying health coverage.'"
The requirement survives, but its federal penalty does not. The Tax Cuts and Jobs Act reduced the payment to "Zero percent" and "$0" for months beginning after December 31, 2018. What keeps the term in use is everything else that is tied to it: the premium tax credit, Marketplace enrollment rules, health coverage reporting on Forms 1095, and state mandates such as California's.