It's a way of making sure that everyone in your project organisation knows exactly what it is they have to contribute, and in what way. It gives a clear understanding that the way roles have been assigned makes the participants of the project interdependent.

It involves identifying and capturing the appropriate information regarding the following elements:
 

• Activity - A brief description of the task being assigned.
• Responsible - The name of the person who owns the resources which allow them to respond
• Accountable - The person you are counting on to deliver...
• Provides Input -  Where will you find the appropriate information, materials etc.?
• Decision Owner - Who has the decision rights associated with this?