Which type of backup saves only files changed since the last incremental backup?

The choice of "incremental backup" is correct as it specifically refers to a type of backup system that only saves the files that have changed since the last incremental backup was performed. This method is highly efficient because it minimizes the amount of data being copied each time a backup is conducted, leading to reduced backup time and storage requirements.

In contrast, a differential backup saves all the changes made since the last full backup, which means it accumulates data over time until the next full backup is performed. A full backup captures all files and directories regardless of any changes, making it the most comprehensive but also the most storage-intensive option. A snapshot backup provides a point-in-time image of the system, allowing for quick recovery but does not inherently focus on the incremental changes. Thus, incremental backups stand out for their efficiency in handling only recent changes since the last incremental backup.