What does Backup Window mean?
A backup window is the time slot/window when it is most suitable to back up data, applications or a system. It is a predefined/prescheduled time when the backup software is permitted to start the backup process on a computer system.
Techopedia explains Backup Window
A backup window primarily helps system/backup administrators to identify, plan and execute the backup process. Typically, the backup window is set for time slots when the backup process will have the most minimal impact on the system's overall performance and/or interference with users' tasks. To enable this, a system's peak and non-peak hours are identified. For example, standard desktop computers within an office typically have peak hours during normal business hours. Therefore, the administrator can select an overnight backup window when the system is generally idle or has minimal workload.