Alex himself took the trip. 

They did the work themselves.

It functions as direct object or object of the preposition.

It simply adds emphasis to a noun or pronoun in the sentence. 

Anna was talking to herself. 

The schemers deceived themselves.

A pronouns that end with -self or -selves. 

He made _____ a pasta. 

The door lock by ______.

She made the dinner ______.