From the Outlook Help file:
"Appointments are activities that you schedule in your calendar that do not
involve inviting other people or reserving resources. You can schedule
recurring appointments, view your appointments by day, week, or month, and
set reminders for your appointments.
You can specify how the appointments in your calendar look to others by
designating the time of the appointment as busy, free, tentative, or out of
office. Also, others can give you permission to schedule or make changes to
appointments in their calendars."
"A meeting is an appointment to which you invite people or reserve resources
for. You can create and send meeting requests and reserve resources for
face-to-face meetings or for online meetings. When you create a meeting, you
identify the people to invite and the resources to reserve, and you pick a
meeting time. Responses to your meeting request appear in your Inbox. You
can also add people to an existing meeting or reschedule a meeting."
