It encodes a mailto: link. Scanning opens the phone's email app with a new message already addressed to you — and, if you set them, the subject line and body pre-filled. The person just hits send.
This tool is part of the AITwo QR code suite. Need a different content type — WiFi, vCard, WhatsApp, PDF, payments, maps, or social profiles — or a colored code? See the full Free AI QR Code Generator — 22 types