Larry and Moe have an exchange relationship .
When we say that Larry and Moe have an exchange relationship, we say that they both follow a simple rule of equal favors or benefits to be exchanged between them. When Larry does something to benefit Moe, he is expecting Moe to do the same in return equally and vice versa. This is called an exchange relationship.
The best example for an exchange relationship is when you go to shop and buy something and in exchange you pay money for it.
