What is a differential backup?

A differential backup is indeed a method that includes all the data that has changed since the last full backup was performed. This means it captures any modifications, additions, or deletions of files that occurred since that time. The key aspect of a differential backup is that it progressively accumulates changes over time until another full backup is taken.

This approach has significant advantages in recovery scenarios, as it allows for a more streamlined process of restoring data. When recovering from a differential backup, you only need the last full backup and the most recent differential backup, which simplifies the restoration process compared to managing a series of incremental backups.

The other options do not capture the essence of a differential backup correctly. For instance, copying all files every time refers to a full backup, while an incremental backup focuses solely on new or changed files since the last backup, rather than referencing the last full backup. Additionally, a backup that exclusively copies deleted files does not align with the principles of backup strategies and misses the crucial aspect of preserving valuable data.