According to Dictionary.com:
In my mind, an impediment is anything that delays a team member from working as efficiently and productively as possible.
- obstruction; hindrance; obstacle.
- any physical defect that impedes normal or easy speech; a speech disorder.
- something immaterial that interferes with or delays action or progress [syn: hindrance]
- any structure that makes progress difficult [syn: obstruction]
If you are a manager and don't know better, you tell people what to do and you find an appropriate point of blame for problems.
If you are manager in an agile environment, then you should also be a leader. In this environment it is your duty to help identify, track, manage, measure, AND REMOVE impediments. Your team will reach their goals if you lead and remove impediments. They don't need to be told how to do their job.