Backup log is a feature of backup applications that records the events that occur during a backup process.
A record of the backup process can be a useful troubleshooting tool in case there is a problem with the backup. If and when a problem occurs during the backup process, the log will record the error messages created by the backup application when the error occurred. These error messages (also called error codes) are typically unique to the backup application that generated them, although some applications may share generic messages or codes to signal an error.
Backup logs can be set to store essentially summary data, such as notification that a file failed to open, but logs can also be set to retain more details of the backup process, such as details about the files that were backed up.