NGINX is a free, open-source, high-performance HTTP server and reverse proxy, as well as an IMAP/POP3 proxy server. NGINX is known for its high performance, stability, rich feature set, simple configuration, and low resource consumption.
Unlike traditional servers, NGINX doesn't rely on threads to handle requests. Instead it uses a much more scalable event-driven (asynchronous) architecture. This architecture uses small, but more importantly, predictable amounts of memory under load. Even if you don't expect to handle thousands of simultaneous requests, you can still benefit from NGINX's high-performance and small memory footprint. NGINX scales in all directions: from the smallest VPS all the way up to large clusters of servers.
Nginx was found to be the second most widely used web server across all "active" sites (18.22% of surveyed sites) and for the top million busiest sites (27.83% of surveyed sites). According to W3Techs, it was used by 37.7% of the top 1 million websites, 49.7% of the top 100,000 websites, and by 57.0% of the top 10,000 websites.