There are 4 types of Order status:

Waiting - this is the default status of Cash (payments not processed by online payment processors) orders. This status means that the order has to be manually checked by admin/dispatcher and manually Accepted or Rejected.
Accepted - this is the default status for payments that are successfully processed by an online payment processor. Most payment processors will send back a signal that a transaction was successful and the software will change the order status automatically from Waiting to Accepted. Note: The system is set to send emails on Waiting status and on Accepted status and this may result in very similar emails sent to the customer. To avoid the 2 emails to be sent closely one after the other you can make a change in the Configuration tab of the online payment processor payment type at the back office > Dashboard > Payment methods > click on a payment method to edit > Configuration tab > Send Email for Pending Status: Yes/No.
Rejected - if an online payment transaction were unsuccessful the order may automatically change to Rejected (depends if the payment processor sends a signal back that a transaction has failed). Admins/dispatchers can manually set orders to Rejected in Order details. An automatic email will be sent to the customer with the new Rejected status. An order will be Rejected also if the system is set to allow cancellations ant the customer cancels an order through the front end booking form or through their account.
Archived - each accepted order will be archived 24 hours after the drop off date/time and an automatic email with a review request will be sent to the customer.

You can rename any of the order statuses via the back office > Dashboard > Translations > click on English to edit (or any other language you are using) > search for the term you would like to change > type the new one on the right side and save.