draft option is often used to make the typesetting result of a class or a package easier to debug. Most classes will add a black box at the end of overfull lines with
draft. Some packages try to speed up the compilation by skipping external files.
draft option usually has a
final counterpart which can be set to a single package if the class is called with
You can find an (incomplete) list of classes/packages with a
draft option in What does the draft mode change?.
Tag all questions with draft that refer to the usage of
draft or the changes made by