They are a web server software application developed by a Japanese company called Nginx that is used to provide fast and reliable service to websites. It was created in 2004 as a free open-source alternative to Microsoft IIS and has since become one of the most widely used web servers globally. A key feature of Nginx is its ability to handle multiple requests concurrently, making it an ideal choice for large-scale websites and high-traffic applications. Its performance, security, and scalability make it a popular choice among web developers and administrators.