1) The document summarizes four bundled payment models established by the Centers for Medicare and Medicaid Services (CMS) to encourage cost reduction, clinical integration, and care management among providers. 2) The first three models involve retrospective bundled payments for either an inpatient stay alone (Model 1), an inpatient stay plus post-acute care (Model 2), or post-acute care alone (Model 3). Model 4 establishes a prospective bundled payment for an entire episode of care. 3) By allowing gains from reduced costs to be shared among participating providers, the models aim to financially align physicians and hospitals in driving down costs through care coordination and less costly interventions.