Blood pressure is a measurement of the force exerted by blood on the walls of arteries as the heart pumps blood through the body. It is recorded as two numbers representing systolic and diastolic pressure, with normal blood pressure below 120/80 mmHg, prehypertension between 120-139/80-89 mmHg, and high blood pressure at 140/90 mmHg or higher. High blood pressure usually has no symptoms but can lead to serious health problems if left uncontrolled, so it is important to monitor blood pressure and make lifestyle changes or use medication if needed to manage pressure.