The input focus determines which window receives the keyboard input. The way in which your standard window manager has been set up for you is called ``click to focus''. This means you have to click on the window you want to give keyboard input. The second way of determining the keyboard focus is called ``auto keyboard focus''. In this mode the window which is currently pointed at by the mouse receives all keyboard input.
To change the focus policy it is necessary to change the window managers resource file.