Question

What is the difference between “at their beach house” and “at there beach house”

Answer 1

The difference is that when you say their your referring to it as it’s owned

Answer 2

At the beach’ refers to the beach as a general location. ‘On the beach’ refers to the beach as the area with the sand and the waters specifically. ‘In the beach’ is used more when referring to indoor locations or places near or within the beach area.