A reverse proxy is a server that sits in front of one or more web servers, intercepting requests from clients. This is different from a forward proxy, where the proxy sits in front of the clients. With a reverse proxy, when clients send requests to the origin server of a website, those requests are intercepted by the reverse proxy server.
Reverse proxies provide a standard layer of abstraction and security. They handle SSL/TLS termination, caching, and compression, offloading these resource-intensive tasks from the application servers. They also obscure the internal network topology from the outside world.
No application server should be exposed directly to the internet. A reverse proxy is the protection layer. We use them for security, header sanitization, rate limiting, and unifying disparate microservices under a single domain namespace.