A constructed language, also called an artifical or planned language or a conlang, is a language created by an individual person or group of people. It is created as a whole, not evolving naturally by being spoken by a group of people over time.
Constructed languages can be further groupep into engineered, auxiliary and artistic languages.
Engineered languages are created for the scientific study of and experimentation with language, or logics and philosopy.
Artistic languages are languages created for aesthetics; languages created for fictional settings mostly also fall in this category. Well known artistic languages include J.R.R. Tolkien's languages and Star Trek's Klingon.