Terraform: what does AssumeRole: Service: ec2 do? : <p>What exactly does this AWS role do?</p>

<p>The most relevant bits seem to be: 
<code>"Action": "sts:AssumeRole",</code> and 
<code>"Service": "ec2.amazonaws.com"</code></p>

<p>The full role is here:</p>

<pre><code>resource "aws_iam_role" "test_role" {
  name = "test_role"

  assume_role_policy = &lt;&lt;EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Action": "sts:AssumeRole",
      "Principal": {
        "Service": "ec2.amazonaws.com"
      },
      "Effect": "Allow",
      "Sid": ""
    }
  ]
}
EOF
}
</code></pre>

<p>From: <a href="https://www.terraform.io/docs/providers/aws/r/iam_role.html" rel="noreferrer">https://www.terraform.io/docs/providers/aws/r/iam_role.html</a></p>
