Route to next approver: the next approver in each approval route is substituting for the employee; a level in the approval route is being skipped.
Named substitute: another employee will substitute for one of the approvers in the route. You must specify the employee who will be the substitute if you select this option.
 

 

All routes: the substitution applies to all of the approval routes where the employee is an approver.
Selected routes: the substitution applies to the routes selected by the user.