A Tell Design Pattern means a Reactive component sends a request to another Reactive component and does not wait or look for that other component's Response. It just fires that Request message and forgets about it. This is why it is also known as Fire-and-Forget Design Pattern.
Akka Toolkit has implemented the same design pattern to send messages between its components (Actors). It has implemented this pattern as the function tell.
We can use this tell function to send a Message from one Actor to another, as shown here:
actorRef.tell(MyMessage)
We can also write the preceding code snippet in another format, as follows, by using one of the useful features of the Scala Programming Language:
actorRef tell MyMessage
Akka Toolkit also has a Tell Operator to perform the same job:
actorRef ! MyMessage
Here, the ! symbol is a Tell Operator...