Trust and Role Definition
When trust is present then roles are better defined. Or is it the other way around? If I know that my teammate is competently handling his part of a job, I can better focus on my own part. This is especially true if my part depends on his part. If we succeed in enough projects together, we will build not only trust in our relationship, but also a better understanding of how our roles specifically complement each other. That is the making of a great team.