An Approver or Admin can approve reports. However, an approver has the option to forward a report that has been submitted to them, to another approver for approval.
If an approver is unavailable to approve reports, they can assign another approver to approve reports on their behalf. These approvers are known as Out Of Office Approvers in Zoho Expense. When you assign an out-of-office approver, all the records that are submitted to you will be auto-forwarded to their Approvals tab through which they can approve the records.