In this podcast, Thomas Domville discusses and demonstrates the VIP Contacts feature of the Mail app on iOS.
Assigning a contact the “VIP” status makes finding email messages from them easier - you can use custom notification alerts for VIP contacts; their messages will be flagged when browsing mailboxes, and also stored in a smart VIP mailbox.
You can assign up to 100 VIPs, and if you use iCloud Contacts, your VIPs are available on any other Apple devices signed in to the same account.