nginx is the high-performance web server, reverse proxy, and load balancer that runs in front of most Linux web applications. It overtook Apache as the most-used web server around 2020 because the asynchronous, event-driven architecture handles tens of thousands of concurrent connections per worker without the thread-per-request overhead Apache had.
Day-to-day nginx work is configuration: server blocks, location blocks, proxy_pass directives, SSL termination with Let's Encrypt, caching, rate limiting, and the surprisingly subtle interactions between try_files, rewrite, and return. Courses cover the configuration language, common patterns (reverse proxy in front of an app server, static-file caching, A/B testing via nginx-level routing), and operational concerns like graceful reloads and log analysis.