title: AWS - IAM Roles and Trust Relationships
body: <p>I an new to AWS and IAM and trying to understand roles and trust relationship.</p>
  
  <p>I fully understand why roles are used, how to create them and their use case.</p>
  
  <p>What I don't get is the trust relationship step.  In almost all the cases I have seen it is a one to one relationship. EC2 needs a trust with EC2. Why is there the extra step?</p>
  
  <p>If I create an EC2 instance and a role that has S3 permissions why isn't that enough?</p>