From GNUstepWiki

A message consists of the method selector (name) and accompanying arguments that tell the receiving object in a message expression what to do.


Action Message

In the Application Kit, a message sent by an object (such as a Button or Slider) in response to a user action (such as clicking the button or dragging the slider's knob).

The message translates the user's action into a specific instruction for the application.

Asynchronous Message

A remote message that returns immediately, without waiting for the application that receives the message to respond. The sending application and the receiving application act independently, and are therefore not "in sync."

Event Message

In the Application Kit, a message to perform a method named after an event or sub-event. Event messages are used to dispatch events to the objects that will respond to them.

Remote Message

A message sent from one application to an object in another application.

Synchronous Message

A remote message that doesn't return until the receiving application finishes responding to the message. Because the application that sends the message waits for an acknowledgment or return information from the receiving application, the two applications are kept "in sync."