The primary purpose of a web server is to store, process, and deliver web content to clients over the internet. When users request a webpage through their browsers, the web server retrieves the requested content, which may include HTML files, images, and multimedia, and sends it back to the user's device. Web servers also handle incoming HTTP requests and provide appropriate responses, including error messages for unsuccessful requests. Additionally, they can support various technologies, such as PHP or ASP.NET, allowing for dynamic content generation and enhanced interactivity in web applications.