Merck & Co., Inc. is a global healthcare company that discovers, develops, manufactures, and markets innovative pharmaceutical products, vaccines, and animal health solutions. The company operates through two primary segments: Pharmaceuticals, which comprises human prescription medicines and vaccines sold to wholesalers, hospitals, healthcare providers, and government agencies, and Animal Health, which offers veterinary pharmaceuticals and vaccines sold through veterinarians and distributors for both livestock and companion animals. The company generates revenue primarily through its major pharmaceutical franchises in oncology, vaccines, hospital acute care, cardiometabolic diseases, virology, and diabetes treatments, while the animal health segment contributes additional revenue through livestock and companion animal health products distributed globally. Merck faces competition from generic manufacturers, biosimilar producers, and other research-based pharmaceutical companies, with patent protection providing material market exclusivity for its core products across major markets.