What is diastole? what is systole?

Diastole is the part of the cardiac cycle when the heart refills with blood following systole (contraction). Ventricular diastole is the period during which the ventricles are filling and relaxing, while atrial diastole is the period during which the atria are relaxing.

Diastole - cardiac cycle when the heart refills with blood following systole

systole - part of the cardiac cycle when the ventricles contract.