Hypertension is a chronic disease. It is usually diagnosed after multiple blood pressure measurements are found to be elevated (how elevated depends on your age and other medical conditions). It is a risk factor for stroke and heart attack, as well as kidney failure. There are usually no symptoms, so it can usually only be diagnosed by screening for it.
If you have hypertension it can be a good idea to have a home blood pressure cuff so you can check your own blood pressure now and then to ensure you are adequately managing it. There are a lot of blood pressure cuffs on the market. In general, wrist blood pressure cuffs should not be used - it should go around your arm. You should also use a validated device - you can find a list of validated devices on the Hypertension Canada website - hypertension.ca. When you take your blood pressure you should be sitting and resting for 5 minutes before starting the blood pressure machine with your arm supported on a table.
The best way of dealing with hypertension is through diet and exercise, but often medications are required, and often several medications. There are several diets that have been shown to be effective in hypertension, including the DASH diet, the Mediterranean Diet, and Vegan diets. Salt consumption is the most consistently linked with hypertension. Link to information on: diet and exercise.