[This is preliminary documentation and subject to change.]
Another important feature of MMC is the snap-in manager. This the console-provided means of identifying available snap-ins and allowing the user to select and then manipulate a snap-in. The console identifies snap-ins by the information you make available through the system registry. This is explained in the section of this documentation called Snap-In Components and the Registry.
The snap-in manager is responsible for presenting a list of available snap-in components and allowing the user to insert or delete properties in the scope pane. The snap-in manager relies on complete and accurate entries in the system registry. Accordingly, snap-ins should be self-registering and should complete this task as part of the installation sequence.
If you are writing a snap in, you need to understand that during this phase of console configuration the console requests the snap-in to optionally put up a configuration wizard for gathering settings during the insertion process. The console passes in the CCT_SNAPIN_MANAGER as a value for the DATA_OBJECT_TYPES.