Or, say you've started your favourite program, but the text gets chopped off at the bottom of the screen. You need a scrollbar.
Or maybe you've managed to start your program and scroll around a bit, but when you want to type in the window nothing happens. Usually, this means that the window does not have the input focus.
Once you're on your way, opening several windows and computing along, you find the screen gets awfully cluttered. Find out how to keep it tidy, by turning your program windows into icons when you don't want to look at them.
The details of how to resize and move windows around are in section 2.2, Window Frame Elements .