In Zendesk, tickets are solved first and then, after they have maintained their solved status for a predefined amount of time (set up in your automations or triggers), they are moved to closed.
The major differences between solved and closed tickets are the following:
Solved tickets can be reopened and updated. Tickets can be marked solved by Agents or End-users. Tickets marked as solved and responded to by an end-user will be reset to an open status.
Closed tickets are locked. They cannot be re-opened or altered. They can only be closed via a trigger or automation.
You can create a follow-up from a closed ticket that will include a link to the closed ticket. For details, see Creating a follow-up for a closed ticket. Note that tickets cannot be closed manually; they can only be set closed via an automation or trigger (or the system batch close, discussed later).
Your Zendesk trial comes with an automation called Close ticket 4 days after status is set to solved. This automation allows your end-users 4 days to respond to a solved ticket before the ticket will be moved to a closed status. You can set this automation to run anywhere between 1 hour and 28 days.
Best practice guidelines recommend that you leave a ticket in solved status for 3-5 days before moving to closed. This allows your end-users to re-engage with you, and their answers will still be threaded in the same ticket. If you move the ticket to a closed state and the user has follow-up questions or needs clarification, their response will open a new (follow-up) ticket rather than thread in the original ticket.
If you deactivate the Close ticket 4 days after status is set to solved automation, your solved tickets will be set to closed via a system action (noted in your events and notifications as a 'batch close') after 28 days of inactivity.