A disk image format is a file format that contains a complete copy of a storage device, such as a hard drive or CD. These files can replicate the entire structure and content of the original media, including files, folders, and file systems. Common disk image formats include ISO, DMG, and VHD, each serving different purposes and platforms. Disk images are useful for backup, software distribution, and virtualization. They allow users to create exact replicas of disks, making it easier to restore data or run applications in a controlled environment. By using disk images, users can efficiently manage and transfer large amounts of data.