This is the 11314th most frequent Korean word.
김복수씨와
"Kim Bok-su and" (a way to address or refer to someone named Kim Bok-su along with others).
The word 김복수씨와 indicates the companion in an activity, specifying Mr. Kim Boksu as the person with whom the speaker had dinner.
김복수씨와 저녁을 먹었습니다.
I had dinner with Mr. Kim Boksu.
In this sentence, 김복수씨와 is used to denote collaboration or partnership in a professional setting, indicating Mr. Kim Boksu as the coworker.
저는 김복수씨와 함께 일합니다.
I work together with Mr. Kim Boksu.
Here, 김복수씨와 highlights interaction in a conversation, specifying that the speaker enjoys talking with Mr. Kim Boksu.