High blood pressure, defined as a systolic pressure over 140 mmHg and diastolic pressure over 90 mmHg, can lead to symptoms like giddiness and headache if left uncontrolled. It can be essential hypertension (genetic) in adults or secondary hypertension in younger individuals due to other health issues. Treatment involves lifestyle changes, such as reducing salt intake, and medications like beta-blockers and calcium channel blockers tailored to individual responses.