Gio-2.0 ▶ Gio ▶ NotificationPrioritySince 2.42

for events that require more attention, usually because responses are time-sensitive (for example chat and SMS messages or alarms)

for notifications that do not require immediate attention - typically used for contextual background information, such as contact birthdays or local weather

the default priority, to be used for the majority of notifications (for example email messages, software updates, completed download/sync operations)

for urgent notifications, or notifications that require a response in a short space of time (for example phone calls or emergency warnings)