"Yes, my mom is at home, too."
Translation:Да, моя мама тоже дома.
дом means "home," whereas дома means "at home." from my understanding, they basically just combined the preposition and noun into one word.
I'm guessing this is another word order-emphasis issue. I'm not sure. However, it is important to note that, in English as well as Russian, different emphasis can slightly alter the meaning of even the same sentence. However in Russian word order, being more flexible, is used to determine emphasis to some degree.