An alternate approver can approve leave on behalf of a primary approver. They will not, however, receive email notification of requests and reports, but they can click on Show Alternate Approvals (Under MANAGEMENT ->Overview) to view requests that have not been approved by primary approvers. This is particularly helpful if the primary approver is not available to approve requests.
Alternate approvers can see how many pending alternate approvals you have as shown:
To see alternate approvals check the box next to "Show Alternate Approvals" and they will be listed along with your other pending approvals: