In some cases, it is desirable for user activity in a replication topology to be treated differently from agent activity. For example, if a row is inserted by a user at the Publisher and that insert satisfies a check constraint on the table, it might not be required to enforce the same constraint when the row is inserted by a replication agent at the Subscriber. The NOT FOR REPLICATION option allows you to specify that the following database objects are treated differently when a replication agent performs an operation: 

•  Foreign key constraints: The foreign key constraint is not enforced when a replication agent performs an insert, update, or delete operation.
• Check constraints: The check constraint is not enforced when a replication agent performs an insert, update, or delete operation.
•  Identity columns: The identity column value is not incremented when a replication agent performs an insert operation.
•  Triggers: The trigger is not executed when a replication agent performs an insert, update, or delete operation.