High Blood Pressure

High blood pressure or hypertension means high pressure (tension) in the arteries. Arteries are blood vessels that carry blood from the pumping heart to all the tissues and organs of the body.
Blood pressure readings are measured in millimeters of mercury (mmHg) and usually given as 2 numbers. For example, 140 over 90 (written as 140/90)
The top number is systolic pressure, the pressure created when your heart beats. The bottom number is diastolic pressure, the pressure inside blood vessels when the heart is at rest. The diastolic pressure reflects the lowest pressure to which the arteries are exposed.
Normal blood pressure is 120/80 mmHg, blood pressure between 120/80 and 139/89 is called "pre–hypertension", and blood pressure consistence to 140/90 mmHg or above are called “hypertension” or high blood pressure.

Risk factors
There are many factors develop high blood pressure.
High salt and high fat diet, too much salt in your diet can lead to high blood pressure.
Obesity, most people with high body weight developing high blood pressure.
Family history of high blood pressure, if your family has a history of the disease, then you are at a higher risk.

How you can control high blood pressure?
Diet control, weight control, preventing stress, routine exercise and alcohol moderation are the best treatment which controlling or preventing high blood pressure. Beside drug treatments of course

Complications
The goal of treatment in high blood pressure is to reduce blood pressure, so you have lower risk of high blood pressure complications.
High blood pressure increases the risk of developing heart disease, kidney disease, hardening of the arteries, eye damage, and stroke. These complications of high blood pressure are often referred to as end–organ damage because damage to these organs is the end result of long duration high blood pressure. For that reason, the diagnosis of high blood pressure is important so efforts can be made to normalize blood pressure and prevent complications.
------------------------------
PS:
Reference
medicine.net-What is high blood pressure (hypertension)?medlineplus.gov- High blood pressure (Hypertension)