One's home country or homeland — the country where one was born/raised or holds nationality; used especially when abroad.
留学していたとき、母国の食べ物が恋しくなった。
While studying abroad, I began to miss the food from my home country.
彼は母国に戻って政治活動を始めた。
He returned to his homeland and began political activity.
母国語と現地語の違いに戸惑うことがある。
There are times when I'm puzzled by differences between my native language and the local language.