The Backup & Sync feature plays a crucial role in managing your Autofill data in IronVest. When enabled, your Autofill data, which includes Login details, passwords, Autofill cards, Identity Profiles, and Addresses, is accessible across various devices and browsers, making for a seamless user experience. However, without Backup & Sync, your Autofill data is stored locally on the browser where it was created and won't be available on a different device or browser.