When ticked this will send an email at 8pm to all staff that have had expenses approved or declined that day with any comments added.
The email template can be found in Setting > Message options > Email copy > Daily expenses breakdown > Edit.
The email will also let them know which expenses are still outstanding if they have any.
This is where you specify the a list of your expense categories that staff can submit their expenses against in their staffarea.
The default list is as follows: