It's the most common and direct way to express love in Korean.
Here's a breakdown of the word:
* 사랑 (sarang): Love
* 스럽다 (seureopda): Adjective suffix indicating "like" or "full of"
* 은/는 (eun/neun): Subject marker, used to connect the adjective to the subject (in this case, "I")
So, "sarangseureoun" literally means "full of love" or "love-like," but is used to express "I love you."