Software representations of real-world objects (we call them user objects) replace applications. Gone are the walls and restrictions of applications, replaced with compositions of user objects that may be assembled by drag and drop.
Here we have an example from the space flight domain. On the ground, engineers track spacecraft health using telemetry. Telemetry means, essentially, to monitor something remotely (tele, meaning long distance, and meter, meaning to measure). Below we see a telemetry object from the space station. It is shown as multiple possible views including a numerical view, a plot, a graph, and an info or metadata view. Each view is a different way of looking at the same thing. Rather than using multiple software applications to view the telemetry in different ways, the user simply selects different views of the same user object.
Adding and removing functionality from MCT is as simple as adding and removing plug-ins from a directory. Want a notebook? Drop the notebook plug-in into the plugins directory. Don't need plots? Remove that plug-in.
User objects may be shared and reused, and since everything the user manipulates in MCT is a user object, practically anything, from a simple visualization, to a complex composite display may be shared and used again in whole or in part.