You can add "Custom Statuses" to your tickets, besides the default ones, which are "New", "In process" and "Resolved". Every custom status has a name and a text-caption, used for the button, that moves a ticket to this status. For example: you can add a custom status named "On hold", with a "Put on hold" button. Or a status named "escalated to management" with an "escalate" button
NOTE: new tickets should be moved to the "in process" status (by assigning a technician or by "taking" it) before you can move them to a custom status.
You can also mark a custom status "for technicians only" so only "agents" can move a ticket to this status, not the ticket-submitter.
This page - lists all custom statuses available in the helpdesk and allows creating new ones.