The Ticket priority is calulated by the SLA applied to a ticket and the Impact and Urgency set on the Ticket.
This proprity is then used to determine the order of Tickets presented to Users and the order Tickets are displayed in the Ticket List.
You can increase or decrease the priority of a Ticket using the Priority Adjustment.
The Priority Adjustment is an additional priority number between 0 and 100. This is used to increase or decrease the priority of a Ticket above other Tickets. The Priority score of the Ticket will still be set based on the Impact, Urgency, SLA etc, but the Priority Adjustment will then allow you to modify the overall Priority of the Ticket.
For instance a Ticket might have a Priority of 20, but in this instance due to the keywords within the Ticket you want to increase this priority. If the Prority Adjstment is set to +10, whilst this Ticket is still a Priority of 20, it will be assigned / listed above any other Priority 20 tickets due to its adjustment.
You can make these Priority Adjustments within Workflows.
In any Ticket Workflow there is an Action for Change Priority Adjustment. This allows you to set a Priority Adjustment which will work alongside the Priority score on a Ticket.
Beacuase this is an Action on a workflow, you can do this on any part of the Tickets lifecycle (Ticket Opened, Queue Changed, SLA set etc)