Nginx (pronounced "engine-x") is a high-performance web server, reverse proxy, and load balancer originally created to solve the C10K problem — handling 10,000 concurrent connections. Unlike traditional servers that spawn a process per request, Nginx uses an asynchronous, event-driven architecture with worker processes, enabling it to handle thousands of simultaneous connections with minimal memory. Today, Nginx powers over 30% of the world's busiest websites, excelling in scenarios requiring high concurrency, low latency, and efficient resource use. The key to mastering Nginx is understanding its hierarchical configuration structure (main → http → server → location) and recognizing that context matters — where you place a directive determines its scope and behavior, making precise configuration placement critical for predictable results.