It's what you need to read for each skill to figure out what's going on. (and unfortunately duo does a bad job showing they're available (and only on the website, and until recently only in desktop view). See my comments above.
A lot of people mention tips and notes. Where are they? I can't find them!
There's a few ways to get them:
Organized by skill in one pdf for the whole course (by the guy who created the awesome Memrise Duolingo vocab course): https://www.docdroid.net/JnfmyEV/tipsnotesbackup.pdf
Or Replace your username where mine is for information on your progress and tips and notes, etc. https://duome.eu/teribleteri/progress
The way duolingo has it set up is only on their website, under each skill, click on the circle and then on the lightbulb icon. Do it under desktop view to see everything the duolingo site offers (the discussions, etc.)
The Memrise Duolingo vocab course has almost every word broken up into skill groups, without vocab and you can hear individual words, not in sentences. http://www.memrise.com/course/1031737/
I use all these links as I'm primarily in the app. The duolingo website is my least favourite way to see the tips and notes.
Update, there's also a Duolingo vocab course to use with ANKI. You can get the files for free in the Duolingo Hebrew learners Facebook group. If you don't use Facebook it might also be available by searching anki files from inside the anki app.
Tips & Notes, daily, weekly rankings and who is following you, is found only in the PC version. Under Home.