Merge pull request MicrosoftDocs#4904 from get-itips/patch-142

Proposing clarifying user desc

Author: kenwith

teams/teams-ps/teams/Add-TeamUser.md

@@ -53,7 +53,7 @@ Accept wildcard characters: False
 ```
 
 ### -User
-User's UPN (user principal name - e.g. [email protected]).
+UPN of a user of the organization (user principal name - e.g. [email protected]).
 
 ```yaml
 Type: String