I know what MSConfig does, and I know it is an abbreviated version of Microsoft Configuration Utility, but what does it actually mean in a "registry key" once I follow this typical path below?
Such as HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Shared Tools\MSConfig\ (usually followed by startupreg or similar terms).
Does it mean it contains empty registry items, or leads to deleted items, etc.?
The configuration information is stored in that location in the Windows Registry. Since the final key, MSConfig, is followed by a slash, it means that it's definitely a key (a container, not a value) that can hold registry values and/or keys (or be empty).
For the benefit of others who may be wondering what this is all about...
MSCONFIG (Microsoft's System Configuration Utility) is a tool that lets you make various changes to Windows, and it happens to be primarily concerned with how Windows starts up. Many of the settings are stored in the Windows Registry (see my next paragraph for more about this...).
REGEDIT (Registry Editor) is a tool that lets you view and edit the Windows Registry, which is a proprietary database that is used to store nearly all settings for the Operating System and most Windows applications.
Because you essentially have full access to every setting in the system, this tool can be particularly dangerous and its use could result in your computer not starting at all (or a wide range of other problems). It is considered to be a tool for users with an advanced level of expertise.
Note: I posted these screenshot images of these tools to satisfy the curiosity of those who also don't want to start these programs due to the risk of causing problems on their computers (hopefully this will help to prevent accidental problems by non-expert users).
The items that appear in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Shared Tools\MSConfig\ are items you have modified or disabled through MSConfig.
These entries are for informational purposes such as the date and time the entry was modified or disabled as well as the key in the registry that was modified. This also allows MSConfig to modify the entry in the future to allow you to re-add something to your startup, service states, etc.
