Here is a decent explanation. It's been covered in a few lessons: http://en.wikipedia.org/wiki/Irish_syntax#The_copula_is
It has taken me until now - four years after this message - to find Tips and Notes on the computer. When you hit a lesson set (say, Basics 1) a rectangle opens below it that tells you which set you're on and how many still to go before you reach level 5.
At the top right of that rectangle is a lightbulb icon. THAT's where I found the Tips and Hints! I could have screamed...
Scroll down on this page for the Tips and Notes. I use the computer and the mobile phone. If you have wifi, you can access the internet page that the computer users see. https://www.duolingo.com/skill/ga/Basics-1
Rumoured, avatars are optional so you cannot assume someone is on mobile by that.
ataltane, the Tips & notes appear on the top left on my computer lesson pages.
I'm not sure what you're asking.
Irish grammar is different from English grammar. English is SVO (subject-verb-object) or SVC (subject-verb-complement). Irish is VSO or VCS.
Word-for-word, "is fear é" is "is man he". Irish also does not have any indefinite articles. In English, we put it as "he is a man".
No, the first lesson did not teach you to say "Is fear sé" for "he is a man" and "Is bean sí" for "she is a woman".
If that's what you wrote down in your notes, the discrepancy is in your notes, because you won't find any evidence of "Is fear sé" or "Is bean sí" on Duolingo.
sé, sí and siad are only ever used as the Subject of a verb, and adjacent to that verb, they are not used with the copula.