Summary

DML triggers should be seen as specialized and specific stored procedures set up to help your system with maintaining data integrity, cascading updates throughout a system, or enforcing business rules. If you take out the fact that there are two system tables, INSERTED and DELETED, and that you can check what columns have been modified, then the whole essence of a trigger is that it is a stored procedure that runs automatically when a set data-modification condition arises on a specific table.

DDL triggers will be built mainly for security or reporting of system changes to compliance departments and the like. With the EventData() XML information available to a trigger, a great deal of useful information can be inspected and used further.