They are all part of the registry’s logical structure.

Keys, values, and data types are all the information contained in the registry subtrees. Subtrees represent the logical structure of the registry. The registry consists of subtrees, keys, values, data types, and hives. If you change your wallpaper or your display settings or install software on your server, Windows 2000 records these changes in the registry. The registry is a database that records and updates any and all settings changes you make on the computer. In this Daily Drill Down, I’ll describe some problems with the system hive of the registry and how to recover from them. If there’s a problem with your server’s registry, chances are your entire network will suffer. It’s a mysterious place of strange spellings, capitalization, and spacing, but it’s also the heart of your server’s configuration. Your server’s registry is the place where angels fear to tread. While the registry can be a forbidding place, you have options for restoring the system hive of your server's registry and avoiding data loss.

If your server has a problem with its registry, then your network will have problems too. Recover the system hive of your server’s registry

Restore registry