AFTER - Specifies that the trigger is fired only when all operations specified in the triggering SQL statement have executed successfully. All referential cascade actions and constraint checks also must succeed before this trigger executes.
INSTEAD OF - Specifies that the trigger is executed instead of the triggering SQL statement, thus overriding the actions of the triggering statements.
2)Instead of triggers that we use generally on view where we want to give only restricted access to table through view.