App Inventor Classic (the original App Inventor) will
shut down 15 July 2015 (
https://groups.google.com/forum/#!category-topic/mitappinventortest/lMko5JCFa7o ). You will
no longer be able to develop the original App Inventor Projects on MIT's server. You need to switch to AI2.
So, please be aware there are many App Inventor Classic online courses still selling their services. An original App Inventor online course is almost useless because of the App Inventor Classic shutdown. You may not want to waste your money paying for such a course. Unless a course indicates specifically it is for App Inventor 2, you may not want to invest in that course.

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OK, some of the translations are amusing and not totally correct, however there are lots of examples that can be followed in the figures in the text.
These are my opinions. Enjoy learning App Inventor 2 . Be careful selecting an App Inventor 2 course if you need more advice than provided in the free course indicated above. Make sure it teaches App Inventor 2.
Regards,
Steve