What is it called when an author uses a different name?

A pseudonym is a fictitious name taken by a writer in place of their real name. The term "pseudonym" is a Greek word that literally means "false name." There are many reasons why an author might use a pen name. A woman writer might have a better chance of getting published if she is thought to be male. This was done frequently in earlier centuries when women were not published at all.

Source: Audible Blog