The "Urgency" field in the Create Request form provides an indication of how urgent the request is to the person for whom the work is being done. It is used to determine a rough starting position for the work in the "Upcoming Projects" part of the work queue, unless of course it's an "Emergency", in which case it's added to the "Emergency" section at the top of the queue.
When specifying this field in a customized sort or display, any of the names "urgency", "Urgency" or "Urg" (for terse output) can be used.