Keep healthy English.

A: HMO is a health insurance system that pays in advance. Regular 24-hour medical service and preventive medical service are usually provided in the form of outpatient service. Its service target is those employees who have to pay their own real-name personal medical expenses in addition to the fixed annual fee paid by the employer. Health maintenance organizations will charge employers (or both employees and employers) a fixed annual fee according to the number of employees, regardless of whether they provide medical services to employees or not.