Web Application Firewall - security system that filters HTTP traffic to web applications. Like having a security guard that checks everyone entering a building and blocks suspicious visitors.
E-commerce websites use WAF to block SQL injection attacks and other malicious web traffic automatically.
All provide managed Layer 7 (HTTP/S) protection for web apps and APIs, using rules (managed and custom) to detect/block common attacks (e.g., SQLi, XSS). AWS WAF commonly attaches to CloudFront/ALB/API Gateway; Azure WAF integrates with Application Gateway/Front Door; Cloud Armor protects behind Google Cloud load balancers and integrates with reCAPTCHA Enterprise; OCI WAF fronts apps via OCI edge and supports managed rules and bot controls.