An On Clause specifies how to handle a particular kind of message as part of the definition of a [handler](/concepts/handler/. An On Clause is associated with a specific message definition and contains an example that defines the handling of that message by the handler’s parent. An On Clause is also optionally associated with an entity or pipe) as the sender of a message.
- Handlers - the handler to which the On clause is applied
- Examples - specifies what should happen when the event occurs