Nginx is a web server that can also function as a reverse proxy, load balancer, and HTTP server. It is known for its stability, performance, simple configuration, rich feature set, and low resource usage. The document provides instructions on how to configure Nginx as a reverse proxy for virtual hosting. This involves deploying Nginx, configuring a domain to point to the Nginx server, creating a configuration file matching the domain name, and modifying the file to proxy requests to the actual application server. Once configured, requests for the domain will be handled by Nginx and routed to the backend application server.