About the database backup, there are two statements in the online help
Backup Database DiffERENTIAL Option Description
Specifying a database backup or file backup should be consistent with a database or file portion that changes after the last full backup. Difference backups are generally less space than full backups. For all single logs for the last full backup, use this option without having to make a backup. For more information, see Difference Database Backup and File Difference Backup.
Description Database Backup Division Database Backup only records data that changes from the last database backup. Differential database backups are small than database backups, so you can backup more frequently, often backups will reduce the risk of losing data.
This is the second statement, let me think that the difference backup is a change that has occurred after the last data backup, and this backup, I have always understood any kind of backup, think of sweating
Reading is not careful, it must be changed
