Home Server Questions

I am a noob when it comes to how servers work but I want to build one?

I want to know what is the best software, Operating System and the most ideal power to use for a home server and how it works etc.

Also I want to know is it wise to build a PC and use it as an FTP Server?

Thank you. Is it silly to be using Windows 7 and Filezilla? Or Linux and Filezilla etc?