A disk image format is a file format that captures the complete contents and structure of a storage device, such as a hard drive or CD. This format allows users to create a digital copy of the entire disk, including files, folders, and system settings, making it useful for backups, software distribution, and virtualization. Common disk image formats include ISO, which is often used for optical discs, and IMG, which can represent various types of storage media. These formats enable easy sharing and mounting of disk images, allowing users to access the data without needing the original physical media.