Differential backup is a type of data backup strategy that involves backing up only the data that has changed since the last full backup. This approach is often used as a way to reduce the time and storage space required for backup operations, as well as to minimize the amount of data that needs to be transmitted over a network during backup and recovery operations.

In a differential backup, the first backup is a full backup that captures all of the data that needs to be protected. Subsequent backups capture only the data that has changed since the last full backup. For example, if a file has been modified or new files have been added, the differential backup will capture those changes, but if a file has not been modified since the last full backup, it will not be included in the differential backup.

The main advantage of differential backup is that it requires less storage space and backup time than full backups, but still provides a relatively comprehensive backup of the data. In addition, differential backups can be used in conjunction with other backup strategies, such as incremental backups, to provide a more comprehensive backup solution.

However, there are some disadvantages to using differential backups. One of the main drawbacks is that recovery time can be longer than with a full backup, since differential backups require more steps to recover the data. In addition, differential backups can also require more storage space than incremental backups, as each differential backup captures all of the data that has changed since the last full backup.

In summary, differential backup is a backup strategy that captures only the data that has changed since the last full backup, providing a more efficient and space-saving backup solution. While there are some drawbacks to using differential backups, they can be a useful tool in a comprehensive backup and recovery strategy.