Do you understand that an OS is intended to control everything a "computer" does? Do you understand the interface of the OS to hardware? Do you understand the interface of the OS to users? Do you know what services it must provide? Do you understand how they are installed? How are they maintained? What are the common OS we find in mobile, desktop, and server based systems?
The questions in the previous paragraph must be answered at a minimum. Just listing "common OS" found in desktop computers doesn't prove you "understand." You need to compare and contrast for example Windows with Linux. Compare the user interface. Contrast the file system structure. If you "ipconfig" in Windows what is the Linux equivalent?