X Window System Basics ( via ) is an interactive walk through of the basic elements of X, starting with windows themselves and various things to do with them. This is a topic that's very relevant to me since I deal with old X programs and an old X window manager that have things like old fashioned iconification of windows . Fiddling around with the interactive demos (which require Javascript) is a great way to see in a concrete way how the nuts and bolts work.