This is the Reminders tab of the Visit Editor. See Concepts - Reminders for background.
 

The buttons are as follows:
OK - save any changes and close the Visit Editor
Cancel - cancel any changes and close the Visit Editor
New - create a new reminder
Edit - edit the selected reminder
Delete - delete the selected reminder - a confirmation window will be displayed

This screen is very similar to the Patients - Medical Records - Reminders tab - see this for further information.