What is a “social” or “update” classification?

Gmail uses specialized categories beyond Promotions:

Social: Notifications from social networks like Facebook, Twitter, LinkedIn. Friend requests, mentions, activity alerts.

Updates: Transactional messages, receipts, order confirmations, shipping notifications, account alerts. Automated but important.

These classifications reflect message type rather than trust level. A social notification is not promotional content. An order receipt is not a marketing message.

Proper classification helps users find messages where they expect them.

Different cargo types go to different warehouses. Social goods to one, manifests and receipts to another.