In general, as a noun, an alias (pronounced AY-lee-uhs) is an alternate name for someone or something. In literature, a "pen name" is an alias for the author's real name. The noun is derived from the Latin adverb alias, meaning "otherwise" and by extension "otherwise known as" and the latter meaning is still used in English, as in: Clark Kent, alias Superman. In information technology, the noun has at least two different usages.
1) In some computer operating systems and programming languages, an alias is an alternative and usually easier-to-understand or more significant name for a defined data object. The data object can be defined once and later a programmer can define one or more equivalent aliases that will also refer to the data object. In some languages, this is known as an "equate" instruction.