If you refer to a couple of people or things, you mean two or approximately two of them, although the exact number is not important or you are not sure of it. 一两个; 几个
noun [抽象名词]两个,几个;一对夫妇,一对情侣
A couple is two people who are married, living together, or having a sexual relationship. 一对夫妇
If you say that one thing produces a particular effect when it is coupled with another, you mean that the two things combine to produce that effect. 与…结合