On the orders overview page you'll see a list with all the orders including the state of an order. Per order your customer can register multiple tickets.
These are indicated with a green label, describing the Payment Method (Master Card, Visa, AMEX, iDeal, Invoice etc).
These are indicated with a Orange or Red label. Red labeled orders are overdue, the number of days is shown in the label as well.
You can read more about this subject on the help page Invoice order details.
These are blue and grey, indicating the canceled order and the associated credit invoice.
Paydro automatically refunds online paid orders.
The attendees from canceled orders are automatically removed from the attendee list.
The online payment failed. You could offer them an invoice payment .
These orders where never finished by your customers. This is a great list to follow up on.