Systolic and diastolic refer to the two phases of blood pressure in the cardiovascular system. Systolic pressure is the force of blood against the artery walls when the heart beats and pumps blood, while diastolic pressure is the force during the resting phase between heartbeats when the heart fills with blood. Blood pressure is typically expressed as systolic over diastolic, such as 120/80 mmHg. These measurements are crucial for assessing cardiovascular health.