Blood pressure represents the pressure of blood in the arteries as the heart contracts and when it is at rest, according to WebMD. The pressure in the arteries right after the heart contracts is called systolic blood pressure, and the pressure when the heart rests is called diastolic blood pressure.
Normal values for systolic and diastolic blood pressure are below 120 and 80, respectively, explains WebMD. Values above 140 for systolic blood pressure and 90 for diastolic blood pressure indicate hypertension. Blood pressure is measured using a blood pressure cuff, also called a sphygmomanometer, which is placed on the upper arm, forearm or wrist.