An Indigo service is a collection of one or more service endpoints. One of our team member pointed out after the initial design phase that understanding Indigo service endpoint is as simple as A, B, C. The A-Address means “Where”, B-Binding means “How” and C-Contact means “What”.

A-Address defines “where” the service is located,
B-Binding defines “how” to communicate to that service and

C-Contract defines “what” to communicate.
 
To learn more about this read the "The Conceptual Overview of Indigo" at
http://winfx.msdn.microsoft.com/library/default.asp?url=/library/en-us/indigo_con/html/3e7e0afd-7913-499d-bafb-eac7caacbc7a.asp?frame=true