Computer servers have operating systems (OS) just like your computer. What you might or might not be aware of is that Windows isn't the only OS there is. Linux is an open source OS that is most commonly used on web servers. It is a very stable and efficient OS that has an added benefit of low cost due to it being open source(free).

Just because you have Windows on your computer that you develop your html pages on does not mean you need a Windows based hosting plan. Your files will work just fine regardless of the platform you put them on. They might be more secure and stable on a Linux system. Unless you will be developing in a Windows based scripting language such as ASP.NET where you would desire a server specifically with windows extensions, there is nothing wrong with using Linux servers.