What is iCloud?

iCloud is Apple's cloud service that backs up your device and keeps photos, messages, contacts, notes and passwords in sync across your iPhone, iPad and Mac. Every Apple ID includes 5 GB free; iCloud+ plans add more storage.

Manage what syncs under Settings → [your name] → iCloud. The most important toggle is iCloud Backup — with it on, a lost or broken phone can be restored to a new one almost exactly as it was.