[This is preliminary documentation and subject to change.]
Many Snap-Ins will support both modes of operation, offering some stand-alone functionality and also extending the functionality of other snap-ins. For example, the Windows NT Event Log snap-in reads the event logs of computers. If the MyComputer object exists in the console, the event log Snap-In automatically extends each instance of a MyComputer object and provides the event logs for that computer. Alternatively, the event log can also operate in stand-alone mode, in which case an administrator must manually provide a computer name when the snap-in is opened, and the snap-in simply provides the event logs of this one computer.
Almost all snap-ins are expected to function standalone, and it's quite common to see snap-ins supporting both modes of behavior. Generally, a snap-in built to support either of these modes is built the same way. The main difference is in how they are registered. Incidentally, the sample snap-in provided with this software development kit is dual mode.