INSTEAD OF Option:

INSTEAD OF triggers gives a transparent way of changing views which cannot be modified directly by UPDATE, INSERT, and DELETE statements. These triggers are known as INSTEAD OF triggers since, unlike other categories of triggers, an Oracle fires the trigger instead of executing the triggering statement.  A trigger performs update, insert, or delete operations straightly on the underlying tables.

Users write normal INSERT, UPDATE, , and DELETE statements against the view and INSTEAD OF trigger works invisibly in the background to make the right actions take place. The INSTEAD OF triggers are activated for every row, By default.