We use I'm home when we have recently arrived at home and are notifying the people we live with. We use at home when somebody asks us where we are on the telephone.

They have mostly the same meaning. I can only think of 1 difference. When you get home, you can say "I'm home" but not "I'm at home." If you're talking to other people, though, and they ask where you are, you can say either "I'm home" or "I'm at home."

" I am at home" generally refers only to the concrete object the "house", thus saying "I am AT home" almost always refers to your place of "dwelling" expressing that you are currently, physically at your "place of dwelling". Such as when you friend calls you to ask where you are at. You should say, "I am AT home." "I am home" can take on a more flexible meaning. It can be a more abstract saying such when returning to your country after a long trip, you could say, "I am home" Or visiting the parents after many years, you could also say, "I am home" even though you are not referring to your actual place of dwelling. But you normally would not say, "I am at home" in these two cases.

"I am at home" could either be an idiomatic expression to express comfort about something or simply telling your currrent location (I rather would say 'I am here at home'). "I am home" - yes I would agree with teacher Kevin Brown. In my opinion, this would also speak of someone's feeling of belonging or expressing that someone has find an answer to what he is looking for. :)

I do not think they have any differences.