Task Notifications and Event Groups
Queues, semaphores, mutexes and event groups are all objects. Each has its own allocation, its own handle, and its own place in the system's RAM budget, and a sender has to be given that handle before it can say anything. The kernel's own header states the distinction plainly: those four are "intermediary objects" for sending an event, and a task notification "is a method of sending an event directly to a task without the need for such an intermediary object."