0 used to show that the people who do the action are also the people who are affected by it -- se stessi, si
2 used to give more attention to the word ‘them’ -- loro stessi
3 used as the object of a verb or preposition when people, animals etc are the object of actions they perform -- se stessi, se stesse, si
4 used to emphasize they, them or the names of people, animals etc -- (essi) stessi, esse (stesse)
They themselves did nothing wrong.
5 without help etc -- da sé
They decided to do it themselves.