A web server is a place that stores, processes, and delivers web pages to Web clients. The web client is nothing but a web browser on our laptops, smartphones, desktops, etc. The communication between the client using the web browser and server takes place using a particular protocol called HTTP called Hypertext Transfer Protocol.

Term Web Server can be referred to as Hardware or software or sometimes both working together. 

Hardware side, the webserver is a computer that stores web server software and website files, such as  HTML documents, images, CSS stylesheets, and JavaScript files.

 A web server connected to the Internet supports physical data interchange with other devices connected to the web network.

The software side of a web server includes several parts that control how web users access hosted files. . An HTTP server is software that understands URLs, commonly known as web addresses. HTTP is the protocol your browser uses to view web pages. The HTTP servers can access by domain names of the websites, and it delivers the content of these hosted websites to the end user’s device.

Web server communication
image courtesy: lastminuteengineers.com

In HTTP protocol, a client initiates communication by making a request HTTP, and the server responds with the content of that web page or error message /404 error. Pages delivered by a server are mostly HTML documents.