The Reminder field is used to configure whether you want to send a reminder for the project activity or not, or if a reminder has already been sent. This activity reminder window is shown for the responsible user when the planned date and time have been exceeded. After the reminder has been sent, this field will display Reminder sent, as long as the receiver has not selected the option Remind me later in the reminder window.
In order to use the reminder feature, this must first be activated per users under the button Reminder in the Users procedure in the Global Settings module.