How do Escalation Rules work in Service Cloud?

Escalation Rules automatically escalate cases that haven't been resolved or actioned within a defined time period. Each rule entry specifies criteria, a time trigger (age over X hours), and the escalation action — which can reassign the case to a new owner/queue and/or send a notification email. The "business hours" setting on an escalation rule determines whether non-business hours count toward the escalation timer. Like assignment rules, only one escalation rule can be active per org at a time.