What is a proxy server?
Answer
A proxy server is an intermediary server that sits between clients and destination servers, forwarding requests on behalf of clients. Forward proxy: used by clients to access the Internet — it hides the client's IP, enables caching (faster access to frequently visited sites), applies access controls, and can bypass geo-restrictions. Common in corporate networks to filter employee Internet access. Reverse proxy: sits in front of web servers, hiding their identities from clients. Used for load balancing (distributing traffic across multiple servers), SSL termination (offloading HTTPS from backend servers), caching, compression, and as a WAF (Web Application Firewall). Examples: Nginx, HAProxy, Cloudflare (reverse proxy/CDN). Transparent proxies intercept traffic without client configuration. Proxies operate at Layer 7 (Application layer), unlike NAT which works at Layer 3.