Which type of backup includes only files that have changed since the last incremental backup?

The type of backup that includes only the files that have changed since the last incremental backup is indeed the incremental backup. In this backup method, after a full backup is made, only the data that has been modified since the last backup (whether that be a full or another incremental backup) is saved. This process allows for efficient use of storage space and reduces the amount of time needed to perform the backup, as it only targets those files that have changed, rather than copying all data again.

This approach also speeds up the backup process compared to full backups and is beneficial in environments where timely data protection is essential. This means that during recovery, you would first need the last full backup and then all subsequent incremental backups to restore the complete state of the data up to the desired point in time.