When you run 'Linux' on the desktop, you are running the Linux kernel with GNU userspace. The GNU project would rather you call it GNU/Linux, to pay homage to their hard work. That is too hard to say, so everybody simply says 'Linux'.

Android also runs the Linux kernel. However, the tools that allow you 'to do whatever you want' are not what you interact with. Android has its own userspace tools designed by Google. These are what you are familiar with. It used to be possible to use a terminal and sort of interact with an Android device like a desktop Linux computer, but that has slowly been disabled overtime.