Explanation/Reference:
The Transact SQL CREATE TRIGGER command creates a DML, DDL, or logon trigger. A trigger is a special kind of stored procedure that automatically executes when an event occurs in the database server.
DML triggers execute when a user tries to modify data through a data manipulation language (DML) event.
DML events are INSERT, UPDATE, or DELETE statements on a table or view. These triggers fire when any valid event is fired, regardless of whether or not any table rows are affected.
Partial syntax is:
CREATE TRIGGER [ schema_name . ]trigger_name
ON { table | view }
[ WITH <dml_trigger_option> [ ,...n ] ]
{ FOR | AFTER | INSTEAD OF }
{ [ INSERT ] [ , ] [ UPDATE ] [ , ] [ DELETE ] }
Reference: CREATE TRIGGER (Transact-SQL)
https://msdn.microsoft.com/en-us/library/ms189799.aspx