It's a very common condition among the population in industrialized countries so do your regular check-up.
NB: Blood pressure is the force of blood against the walls of arteries as the heart pumps blood through the body*
Hypertension could be either primary (also known as essential hypertension) or secondary hypertension.
Primary(essential) hypertension has no identifiable cause so life style modification is essential in the management.
Secondary hypertension on the other hand is hypertension with identifiable cause - causes could be diseases or even medications. (pregnancy, renal diseases, endocrine causes, congenital cardiovascular malformation)
Hypertension could be mild, moderate or severe depending on the readings.
Malignant hypertension or accelerated phase hypertension occurs when blood pressure (BP) rises rapidly and is considered with severe hypertension(based on the readings) and it needs be treated as emergency as it could lead to organ damage - Symptoms: severe headaches, visual, disturbed consciousness...
Pregnancy-induced hypertension also known as gestational hypertension is diagnosed if the blood pressure of a pregnant woman after twenty weeks of gestation is more than 140/90 on two separate occasions with more than six hours interval, without protein in urine.
Check yourself regularly...
*Death in hypertension could be caused by cerebrovascular complications, coronary artery diseases, renal failure... All these are complications if hypertension or the cause of hypertension is untreated*