There is a long-term force of the blood against your artery walls which is high enough that may eventually cause certain health problems like heart disease. 

Understanding Blood Pressure-

Body’s blood pressure is determined by the amount of blood your heart pumps and the amount of resistance to blood flow in your arteries. Now, the scenario is that more blood your heart pumps and the narrower the arteries, the higher is the blood pressure. The reading of blood pressure is determined in millimeters of mercury (mm HG).
There are two numbers:

Top number (systolic pressure):
The first, or upper number measures the pressure in your arteries when your heart beats.

Bottom number (diastolic pressure): 

The second, or lower number measures the pressure the blood is exerting on your arteries between the beats.

The Standard normal value is- 120/80 mm HG.

Now when these pressures are high enough above 120/80 mm HG, then the condition is called Hypertension. And when it is less than the standard value, it is called Hypotension.