In the theory of western music, a mode is a type of musical scale coupled with a set of characteristic melodic behaviors. For example, the gregorian mode (greek mode) is a mode used for classification of Gregorian chant.
In Jazz, from around the 1960’s, modern modes has been used. The first method is to use as an available note scale in certain code. The second method is to use mode as a tone, and to phrasing and harmony on it. In the second method, emphasis is placed on the dominant tones and characteristic sounds.
In modern times, mode is used for the purpose of escaping from music by traditional narrow sense of tonality, that is, major and minor. For this reason, Ionian is not used because it makes it feel like a major tonality which is too much conventional tonality.