A Web Server is software that runs as a daemon on a computer server, it listens for client requests and returns web pages as directed.

Since these are often public services, all connections are accepted and are allowed to make requests. Popular web server software titles are Apache HTTPD, and NginX. Some people use Microsofts IIS.

Programming Languages like Node.JS and Python have their own web servers built into the the language interpreter.

When you use Web Browser software like Firefox or Chrome on your computer, and enter a web address that starts with https:// or http://, they connect to Web Servers to download web pages or web applications for you to read or use. The Web Browser (or web client software) communications with the Web Server.

You can run Web Server software on your own computer (list of web server software). Most of the good ones are free open source software, but they can be a lot of work to setup and maintain. For websites you want to represent your business, contract a Web Hosting service provider to do this work.