...
The System is a URI that identifies the code system that defines the code. If the code is taken from a code system resource then the URL for the code system should be used to represent the System. SystemName is a readable name for the System. Version SystemVersion identifies the version of the System.
Description provides a readable name or designation for the concept identified by the code. Its use is optional and is not intended to be used as a display value or to replace the Decode value for a CodeListItem.
...