By default, you are the only person attending this meeting. When you are meeting with a client, customer, or vendor, it is largely up to you if you wish to add the attendee here in the list. For our purpose, we will add Mike Smith to the list of attendees. Odoo will automatically search in real time as you type out the name.
Odoo will then add the attendee to the attendees list. For internal communications, this can be used to make sure all of the necessary team members are notified of the meeting if they are also using the Odoo schedules.
Odoo will provide you a warning if you add an attendee that does not have an email address. In this case, Odoo will still add the attendee, but naturally any automated notifications cannot be delivered to the attendee.