Types of Contracts

There are 3 types of Contacts in indigo but I feel that we as developers will be using only the above 2 from the list below
1- Service Contract
2- Data Contract
3- Message Contract

Service contract defines the operations (functions) to be exposed to the outside world. Data contract define the data members to be sent and Message Contract defines what part of Data will be in the header and what part will be in the Body of the Message.