I'm afraid I have to disagree. Linux is not complex, not unless you want it to be. On the kernel level, everything is fairly simple.
It works something like this:
Say you type "$>mkdir bob" in the inner workings of bash, this becomes mkdir(bob). Then, this gets passed to the kernel as sys_mkdir(bob), and the kernel then passes it to the file system, which examines the argument, then asks the kernel to pass a message to the HD driver to spin up the hard disk and write to a specified sector of the disk. The driver then passes a message to the kernel indicate success or failure of the operation, which passes a message to the bash shell, which then indicates to you whether or not the directory was created. if all went well, your directory was created. See. Not complex, it can all be broken down
If anyone sees anything wrong with this ^ please point it out. I've only been working with linux for a year or so, so I'm pretty new