What is the range of normal blood pressure? What do the two numbers represent?

I don't have the book but this should help,

When your heart beats it pushes blood into your arteries. This leads to a temporary increase in the pressure in your arteries as the blood is pushed through. This is the higher number, or systolic pressure. Between heart beats the pressure drops, and this is the lower number or diastolic pressure. For example for a reading of 120/80; the pressure of 120 mm Hg (systolic) is the maximum (peak) pressure as the heart pumps into the large arteries, and the pressure of 80 mm Hg (diastolic) is when the heart is between beats and so no blood is being pushed into the large arteries.

Normal blood pressure is generally below 120/80 (one-twenty over eighty). 120 represents the systolic measurement and 80 represents the diastolic measurement.

Blood pressure reading below 120/80 is considered normal.

The two numbers that measure your blood pressure are written like a fraction: one number on top and one on the bottom -- for example, 128/82. The number on top is called the "systolic pressure." Systolic blood pressure measures the pressure inside your blood vessels at the moment your heart beats. The number on the bottom is your diastolic pressure. Diastolic blood pressure measures the pressure in your blood vessels between heartbeats, when your heart is resting.