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 ticket status. The ticket status will remain "New."
Waiting on Customer: The tickets whose statuses are set to "Waiting on Customer".
Open: When an agent replies to a "New" ticket, the ticket status changes to "Open."
On Hold: Tickets can be put "on hold" while we wait for information. For example, let's say that a customer is having trouble with credit card processing. The agent inquired with the payment processing company. While the agent waits to hear from the credit card processing company, the ticket will be "on hold."
Closed: Tickets can be marked as Closed by the members.
Spam: Tickets created by blocked users will be marked as spam. Agents can also mark tickets as spam.
Trash: Irrelevant Tickets can be moved to the trash.