What is Reverse Phase and Normal Phase HPLC techniques ??

HPLC is basically consist of two types of separation techniques I.e. Normal phase and Reverse phase techniques....;

In normal phase HPLC techniques the stationary  phase is  polar in nature and mobile phase is non polar in nature

The vice versa is true for the Reverse phase chromatography in which stationary phase is non polar and mobile phase is polar in nature...one of the such common example is the combination of C18 bonded silica as stationary phase and methanol as mobile phase....