Disk management is a system tool used in operating systems to manage storage devices like hard drives and solid-state drives. It allows users to create, delete, format, and resize partitions, which are sections of a disk that can be used to store data separately. This helps in organizing files and optimizing the use of available storage space. Through disk management, users can also assign drive letters, which are labels that help identify different storage devices. Additionally, it provides options for troubleshooting issues, such as checking for errors or converting file systems, ensuring that the storage devices function efficiently and reliably.