LoTR - “Lord of the Rings” is all three movies.
Not to be confused with the first book... “Fellowship of the Ring”.
So yes, they filmed all three at the same time initially, before the release of FoTR. They did some reshoots and additional scenes “pickups” for each of the other two in between the movies, but the primary filming was already done. Make sense?
Yes it does. It just seems like 16 months wouldn’t be long
enough for such a long trilogy.