Each time you run the overdue approvals function, the program checks for all open approval entries that are currently overdue. For each different approver that has at least one overdue approval entry, the program sends a mail with the list of all their overdue approval entries. The mail will be cc-ed to their approver and all the senders of the overdue approvals. This helps if the overdue approval entry needs to be delegated to a substitute.
Depending on your approval setup, approval notifications may include a list of all outstanding approvals, and not just the new one currently requiring approval. The notification will be SMTP-mail based.
The Last Run Date field shows when the overdue approvals function was last run.