A server that sits in front of web servers and forwards requests to them, providing load balancing and security. Like a receptionist who directs visitors to the right department.
Nginx acts as a reverse proxy, distributing incoming website traffic across multiple servers and hiding their actual locations for security.
A reverse proxy is a pattern rather than a single product. Cloud equivalents are typically L7 load balancers (reverse proxies) often paired with CDN and WAF for caching and security. Some services (e.g., CloudFront/Front Door) act as global reverse proxies at the edge; others (ALB/App Gateway/GCLB/OCI LB) operate regionally in front of application backends.