An HTTP server is a software application that processes requests from clients, typically web browsers, and serves them web content. When a user enters a website address, the browser sends an HTTP request to the server, which then retrieves the requested files, such as HTML pages, images, or videos, and sends them back to the browser. These servers operate using the Hypertext Transfer Protocol, which defines how messages are formatted and transmitted. Popular examples of HTTP servers include Apache, Nginx, and Microsoft IIS. They play a crucial role in delivering web content efficiently and reliably to users around the world.