Health maintenance organization
A health plan that limits care to an in-network provider set, typically with a primary care gatekeeper.
HMO (Health Maintenance Organization) plans are common in the US and some other markets. Care outside the network is usually not covered except in emergencies. Elective medical travel is almost always outside HMO coverage.
What a term means for you depends on your own reports. Ask your treating doctor, or send your reports for a free review.