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 Alternative (Under Dashboard) 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 highlighted below:
To configure an alternate approver for a team, please see here.