Fòram na Gàidhlig

Hello,

"Tha e a' dol dhachaigh" or "Tha e a'dol aig an taigh"
Is there any difference?
Thank you very much for you help

The second one is just wrong. Or rather, it means something totally different. I doesn't mean he's going home(wards). It's conceivable that in the right context this might mean it is happening/going on at the house.
You can only use aig an taigh in the sense of "home" when you're talking about stationary position i.e. tha Màiri aig an taigh = Mary is at home (she's already there, not travelling to or from it)

Ok thank you very much! That's now very clear!
tapadh leibh!

'S e do bheatha!

In fact, I'm always thinking about this.
If I understand well, there are some prepositions for the motion, and preposition for the stationnery.
in french we say "aller à l'école" (to go to school) and "travailler à la maison" (to work at home) with the same à but in gaelic I can use aig for "à" just without motion.
with motion I can say
"Tha mi a'dol dhan doras" or "Tha mi a'dol gus an doras"
That's correct?

dhachaigh is a special case -it's dhachaigh with motion and dachaigh without motion.

the difference bewteen do and gu is more sublte, since both of them mean motion. Thinks of do as "to and into".

Ok, tapadh leibh!
It seems more complicated that I was thinking
i suppose I will understanding more all this subleties with time