A global application delivery platform that combines HTTP/HTTPS load balancing, CDN, WAF, and application acceleration. Operates at layer 7 (HTTP) at global scale.
AZ-104 distinguishes it from Traffic Manager (DNS, layer 4) and Load Balancer (layer 4, regional). Front Door is the global solution for web apps needing high availability and built-in security. Equivalent to AWS CloudFront + ALB + WAF combined.
Azure Front Door is a concept that can show up on the exam. Check the full guide to see it in context.