Firstly qualitative data, which is not based on some measurable, quantitative value is more idiographic. This is a Kantian term and it is used to denote research which focuses more on explaining and understanding the meaning of various cultural phenomena and even subjective one. Generally of some unique phenomena.
Secondly the quantitative data is based on something that can be measured and has some numerical, statistical value. Quantitative data tends to be nomothethic, another Kantian term which is described as a tendency for creating generalizations and it is used in natural sciences mostly. Its focus is find out laws related to objective phenomena.