International Auxiliary Language. General term for invented languages designed for use as international "common languages" to be used by people who don't speak the same language (Esperanto being the most famous, and one of the most pathetic, examples).
Definite article in English, usable for nouns of any number or in any position in the sentence (subject, direct object, indirect object, etc.). It indicates that the following noun is a certain particular noun (or nouns) rather than just anything of its sort.