A pseudonym is a fictitiously chosen alias that has nothing to do with the real name.
Pseudonyms are used to anonymize the real name. The pseudonym stands in place of the real name and does not allow any conclusions about the name or the person hiding behind the pseudonym.
Pseudonyms stand for nicknames and fantasy names. They are used in literature and art to disguise the actual author, writer or artist. On the web, pseudonyms are used in chats and blogs to avoid revealing one's identity. One pseudonym used in chat is the IRC pseudonym, which is managed in nick servers.