You can tell the difference between a meeting and an appointment by the meeting icon.
A meeting is similar to an appointment, only it includes other people and a meeting location. A meeting in your calendar could be one you organize, or it could be one you’ve been invited to by someone else. Meetings appear in your calendar and in the calendars of the other people who are involved.
A meeting in Outlook is set up with the help of a meeting request, which is delivered to the meeting participants via e-mail.
If you're interested in learning more about meetings in general and about the specifics involved in creating or responding to meeting requests, take the course Organize meetings with Outlook.