Required -v- Optional attendees - ? is the difference

[viv]

I can't see any difference. When you are invited to a
meeting, I can't see how you can tell whether you are
considered 'optional' or 'required'. If you accept, your
calender is marked & free/busy time is 'busy'. If you
decline, nothing goes in your calendar.

 

[Sue Mosher [MVP-Outlook]]

There's no functional difference, but some people like to be able to
distinguish them.