The core KB Support plugin comes with three standard statuses that can be assigned to a ticket.
In some environments, additional statuses may be required and for that reason, the Custom Ticket Status extension exists.
With Custom Ticket Status, you can create as many additional statuses as needed. Once created, tickets can be placed into those statuses as needed.
Furthermore, when creating a new status, you have the option to generate a customer email at the time the ticket is placed into the status. Defining the subject, header and content of the email will result in the customer being emailed as soon as the ticket is placed into the status.