fixes issue ubuntu#250 add a glossary description for Command Line Interface

I find this to be a short and effective definition but would appreciate feedback. Thank you.

Author: jade-abc

docs/how-ubuntu-is-made/concepts/glossary.md

@@ -305,7 +305,7 @@ Code Review
 
 CLI
 Command Line Interface
-    *Work in Progress*
+    An interface for interacting with an {term}`OS` and its installed applications via text based commands.
 
 CVE
 Common Vulnerabilities and Exposures