When it comes to web development, it's important to understand the operating system (OS) that the web server is running on. Different operating systems have different capabilities, limitations, and configurations that can affect how the website functions, and also has an impact on liability of web hosting.

The underlying web server OS such as Linux, Windows or Mac can provide different types of programming languages that can be used to build websites. For example, LAMP (Linux-Apache-MySQL-PHP) is the most popular development stack on Linux Operating systems, while .NET framework (Windows-IIS-MSSQL-C#) is used on Windows. On MacOS, you can have similar development stacks used in Linux operating systems as the core of MacOS is similar to Linux.

Knowing the web server OS can also be helpful for security purposes. Some operating systems may have better security features or more frequent security updates than others, which can impact the risk of hacking or data breaches.

While it's not strictly necessary to know the web server OS in all cases, having this knowledge can be useful for web developers, system administrators, and anyone else involved in the management or optimization of a website or web application.