Qt project has very thorough documentation. For each API item (class, method, and so on), there is a section in the documentation that describes that item and mentions things that you need to know. There are also a lot of overview pages describing modules and their parts. When you are wondering what some Qt class or module is made for or how to use it, the Qt documentation is always a good source of information.
Qt Creator has an integrated documentation viewer. The most commonly used documentation feature is context help. To try it out, open the main.cpp file, set the text cursor inside the QApplication text, and press F1. The help section should appear to the right of the code editor. It displays the documentation page ...
