What's happening is that, as we have seen already, the message box is a very special object. We can also use it to send things to the [receive]
objects, or as in this instance, communicate with Max itself using the semicolon. Look at the Message_box_morefeatures.maxpat
patcher depicted in the following screenshot:
Here, some possibilities are shown that arise from the semicolon notation. For more information about what we can do by communicating with Max itself, visit http://cycling74.com/docs/max6/dynamic/c74_docs.html#messages_to_max, or simply click on the big message box on the top of the patcher; it opens your default browser, leading directly to that site.