Hello Amirali1383koohi,
Here "고향" is translated as "hometown". "이" is a particle that is comes after a noun to denote a subject and is equivalent to the be-verbs in English (am, is, are...). "
The first sentences provided should be correctly written as "고향이 어디여요?", and it means "where is your hometown?" "서울이에요" is translated as 'It is Seoul".
Hope this helps.