How can we specify between 'went to A restaurant' and 'went to THE restaurant', which could be different meanings, when the article is 'au restaurant'? Maybe I missed something in a previous explanation or another phrase's comment.
"au" is the contraction of à+le (= to the)
to a restaurant = à un restaurant
In this particular case, I'd have to say context.
But, by curiosity, what would you say is the big difference between "to A restaurant" and "to THE restaurant" if you don't name the restaurant?
when you learn in small segmants, the context is left for our imagination. If "au" was used, we can only imagin the apt context in which it was said. ("around the corner" "in that picture" etc...) I find it helpful for me in order for the phrasesto stick in my memory. Still, I have yet to come up with a context for "non, les vingt canards" :)
Why does the past tense here ia constructed by sont + verb, and in other places by a/ai + verb
French compound tenses can use 2 auxiliaries: "avoir" or "être".
"Aller" is an "être" verb: je suis allé(e), tu es allé(e)...
"Mes parents sont allées au restaurant" should also be accepted in the interest of inclusivity.