Nginx (pronounced "engine-x") is a high-performance, open-source web server and reverse proxy server software. It is designed to handle and efficiently serve static and dynamic content on the web. It is known for its scalability, speed, and ability to handle high levels of concurrent connections.

Originally created by Igor Sysoev in 2004, It has gained popularity over the years due to its lightweight architecture and efficient resource utilization. It can be used as a standalone web server or deployed as a reverse proxy in front of other web servers to distribute incoming requests and improve performance.

It is often used as a load balancer, distributing client requests across multiple servers to enhance reliability and scalability. It supports various protocols such as HTTP, HTTPS, SMTP, POP3, and IMAP, and can also act as a caching server to improve the delivery of static content.

One of the key advantages of Nginx is its ability to handle a large number of concurrent connections while consuming minimal system resources. This makes it suitable for serving high-traffic websites and applications. Additionally, it offers configuration flexibility, allowing administrators to fine-tune its behavior and customize it according to their specific requirements.

Nginx has become a popular choice for many web developers and administrators due to its performance, scalability, and extensive feature set. It is widely used by major websites, web hosting providers, and content delivery networks (CDNs) to optimize web server performance and improve the overall user experience.