When you create calendar entries, they must fall into one of five categories:
An Appointment is an entry in your calendar that does not include the process of inviting others in Notes. Appointments can have a start and end time, can be set to repeat, and can be marked private so that even those with access to your calendar cannot read the particulars about private appointments.
An Anniversary is an occasion that has no time value, such as a birthday, working holiday, or payday. Anniversaries do not affect your free time. Anniversaries appear on your calendar only and can be set to repeat.
All Day Events have a duration of at least one full day. Unlike appointments and invitations, you cannot specify a start time or end time. Events are typically used to schedule vacations, seminars, conventions, and the like.
Reminders are notes to yourself that display on your Calendar on the time and date you assign to them. Reminders have a beginning time but no time value (that is, no ending time). They display on your Calendar only and can be set to repeat. One common use is a reminder to make a phone call. Do not confuse Reminders with Alarms or To Do's.
Meeting Invitations are appointments in which you invite others. Meeting Invitations are distributed to the participants' Inboxes. Meetings also appear on the Calendars of invited participants when the participants are in a Notes organization/domain and have accepted the invitation. Like appointments, meetings have time values, have a beginning time and ending time within one calendar day, and can be set to repeat. You can send meeting invitations to people over the Internet and they will receive a text message, but not all of the formatting and graphics you see in the Notes form.