copyright 2009, The Washington Post Employer Mandate: A requirement that all employers, or at least those of a certain size, offer health benefits that meet a specific standard and pay a set portion of the cost of those benefits on behalf of employees. Individual Mandate: A requirement that all individuals obtain health insurance. A mandate could apply to the entire population or just to children, or could exempt specified individuals. Pay or Play: A requirement that employers declining to offer health benefits pay a specified amount or percentage of payroll into a designated public fund as a source of financing for uninsured workers. In a variation called the 'free rider' provision, employers would be required not to offer health care but to cover the cost of federal subsidies for lower- to middle-income employees who receive coverage through a government insurance exchange. Comparative Effectiveness: The effort to use research and electronic medical records to determine which treatments work best. MedPAC: A commission of health professionals advises Congress on setting Medicare rules and reimbursement rates. Proposals call for empowering it or creating a new executive branch commission to oversee Medicare. Exchange: The insurance marketplace that would be created under all current proposals, in which the uninsured and small businesses would go to buy coverage. To offer plans on the exchange, insurers would have to comply with regulations forbidding practices such as denying coverage because of preexisting conditions. The hope is that pooling risk in one marketplace would lower rates for the uninsured and for small businesses. Public Option: A government-run insurance plan that would be offered on the exchange alongside private insurance plans. People would pay premiums, as with a private plan. It would probably pay providers at rates above Medicare's but below what private insurers pay. 