A web server software makes a computer act like a web server. When you send a request to a web server, for example, requesting to open a web page in a browser, the browser contacts the webserver, And the webserver starts to search for the file you requested as a page and sends it to the browser. This mechanism is called a simple thread request. Formerly, the web servers created a single thread for every request. And this approach doesn't work for high-traffic websites today; it made a situation called the C10K problem. A single thread web server can support only 10,000 connections simultaneously, not more. Therefore, a new generation of web server software such as NGINX came to the front to handle simultaneously many requests with their asynchronous and event-driven architecture.