Here is the list of all the various statuses a ticket is allowed to have out of the box. You can create more ticket statuses. However, you can't delete or rename any of these statuses.
New - This is the default status for the new tickets. It means that no reply has been sent to these tickets. If a new ticket is assigned to an agent then that does not change the status of the ticket. The ticket status will remain "New".
Waiting on Customer - When an agent replies to a ticket then, by default, the ticket status changes to "Waiting on Customer".
Open - When a customer replies to a ticket the status of that ticket changes to "Open". This indicates that the ticket is on the agent's court and the agent needs to reply to the ticket based on the information provided by the customer.
On Hold - Tickets can be put "On Hold" while we wait to get some information. For example, let's say that a customer is having trouble with credit card processing. The agent sent an inquiry to the payment processing company. While the agent is waiting to hear from the credit card processing company the status of the ticket will be "On Hold".
Closed - Tickets can be marked as Closed by the members. When a ticket is marked as “Closed” and the customer replies to it, it will NOT be marked as “Open”, to make that happen, you need to change the config in Settings > Tickets. One thing to note would be that the automation rules don’t work on the “Closed” tickets.
Spam - Tickets that are created by blocked users will be marked as Spam. Tickets can also be marked as spam by agents. The tickets that are in Spam for more than 30 days will be deleted automatically.
Trash - Tickets that are irrelevant can be moved to the trash. The tickets that are in the Trash for more than 30 days will be deleted automatically.