When do you use in and when do you use at?
Do we use "in" when we say:
I live in New York. ?
Then why do we say:
I'm at home.
I'm in school. We say "I am at school" in BrE.
Please give me a descriptive explanation.
New York is a physical place, it's a city, we say that we are in a city.
"Home" is an abstract concept. Your home could be a house, a flat, a mobile home, a cave, etcetera. You are at home or in your house, flat, cave etcetera.