Reaktor/Tutorials/Reaktor as effects processor/Macros
Macros (documents with suffix .mdl) have an icon with three modules linked together, and are self-contained structures that hold other patched-together objects (including instruments, other macros, and modules), just like instruments.
The difference is that macros don't have their own snapshots or panels. They're designed to organize various parts of a complex instrument or ensemble into sub-devices, all of which will be controlled by a single snapshot taken by the containing instrument. An outline around a portion of the controls on a R panel tells you you're looking at a macro that's inside the structure of that instrument, if the panel designer chose to make the macro outline visible, using the Properties window described later in this tutorial.
Modules are R documents at the lowest level. They're the basic building blocks of all the other objects. Each module has its own unique icon, if there's room for an icon on it. Modules can't be opened and they don't have structure windows; they are configured using the properties window (Mac/PC: F4), as you'll see in the Properties portion of this tutorial. Reconfigured modules can only be saved by saving an object that contains them, not on their own, but once reconfigured, they can be copied and pasted.
All other R components can be opened and altered in a new structure window by double-clicking on them.