What's the difference between FOR
and AFTER
triggers?
There is no difference, they do the same thing.
CREATE TRIGGER trgTable on dbo.Table FOR INSERT,UPDATE,DELETE
Is the same as
CREATE TRIGGER trgTable on dbo.Table AFTER INSERT,UPDATE,DELETE
An INSTEAD OF
trigger is different, and fires before and instead of the insert and can be used on views, in order to insert the appropriate values into the underlying tables.