Outlook 2007 – Calendar 4 Kinds of Entries for the Calendar
An APPOINTMENT is an event that only impacts you. This would be used for an appointment, lunch date, workout, etc.
A MEETING is like an appointment, but you are inviting others to attend. By inviting other people, it will automatically show up in their calendar. They can accept or decline the invitation.
An ALL DAY EVENT allows you to mark something that will last all day, but does not take up the whole day so you can make appointments throughout the day. In this example, it is a conference. It would also be used for a birthday, anniversary, etc.
A TASK is something you need to get done, but is not associated with a specific time of completion. On the due date, it will show up below your calendar. If you make a daily list, it will show up there.