There are three possible things a window manager will do when a new window is created. It is possible to configure a window manager so that an outline of the new window is shown, and you are allowed to position it on your screen. That is called ``manual placement''.
It is also possible that the window manager will place the new window somewhere on the screen by itself. This is known as ``random placement''.
Finally, sometimes an application will ask for a specific spot on the screen, or the window manager will be configured to display certain applications on the same place of the screen all the time. (For instance, I could specify that I want xclock to always appear in the upper right hand corner of the screen.)