Barebone systems are partially assembled computer systems that provide the essential components needed to build a functional computer. Typically, they include a motherboard, power supply, and a case, but they lack other components like a processor, memory, and storage. This allows users to customize their systems according to their specific needs and preferences. These systems are popular among enthusiasts and professionals who want to create a tailored computing experience. By choosing their own CPU, RAM, and hard drives, users can optimize performance for tasks such as gaming, video editing, or server management.