IsEscalated(Escalated) field in Salesforce:

IsEscalated field is used as part of Escalation Rules.

When the Case is escalated by the Escalation Rule, it will display the Escalation icon and set Escalated check box to true. The escalation icon disappears when a case is closed or no longer meets escalation rule criteria.

If there is no active Escalation rule and when the Case is closed, the Escalated flag will be set to false.