Its become almost essential for any IT professional to be able to setup a web server nowadays. While the advent of so called personal web server solution stacks (such as XAMPP) have aided testing/development its still necessary to understand a number of concepts in order to configure it.
First, a web server is just a means of delivering of static/non-static content to an end user via computer networking.
Second, content is going to be delivered form a single actual directory which is 'pointed to' via DNS records on the Internet to a physical/virtual host.
Third, through the advent of Virtual Hosts many web servers are often able to serve more than website at a time (based on IP and/or name).
Fourth, the basic web server is often able to only host basic content or needs to be reconfigured in order to provide additional functionality. For example, you may require additional modules such as MySQL or a 'Handler' in order to provide for this.
Fifth, not all web servers are created equal. Like most other products and services, a web server can be designed with certain parameters in mind such as speed, security, or even certain technology frameworks. These additions can be particularly important in deciding which server you may end up choosing depending on the circumstance/s. For example, so called application servers which can have fairly specific capabilities that are not often available in conventional web servers.