GMC is the single group policy an employer buys to cover its whole workforce for in-patient hospitalisation, instead of each employee buying their own. It's the backbone of the benefits programme - the thing people mean when they say “my company insurance.” Because it's a group contract, cover is granted without individual medical underwriting: everyone is in from day one, pre-existing conditions and all.
The employer negotiates the terms - sum insured, who's covered (employee only, or spouse + kids + parents), room-rent rules, maternity, and any special conditions - with an insurer, usually through a broker.
In India
Almost every mid-to-large Indian employer offers GMC; it's a near-universal expectation for white-collar hiring. Parental cover (including in-laws) is a distinctively Indian ask. Premiums are driven by your own claims history - see Incurred Claims Ratio.
In practice
A 500-person firm buys a family-floater GMC with ₹5 lakh sum insured per family. A new joiner's spouse is hospitalised in week two for appendicitis - fully covered, cashless, no waiting period, because group policies waive the individual underwriting a retail policy would apply.