Action description – Descriptive text that can be used to identify this particular action in the Actions list.
Key to create – Defines the registry hive to create the key in. This value, combined with the specific key property locates the new key in the registry.
Type to specify a key – The sub path under the defined hive to create the key. The entire key path is created. The initial \ in the path can be omitted or not.
Expansion variables can be used to set the key to create sub path.
See Create Registry Key for more information