「おめでとう」は、いいことがあった人にお祝いの気持ちをつたえる言葉です。

"おめでとう" is a word used to express congratulations to someone who has had something good happen.

たんじょう日や新年など、たのしいときによく使います。

It is often used during happy occasions like birthdays or the New Year.