Hypertensive emergencies require immediate blood pressure reduction to prevent end organ damage. They are characterized by severely elevated blood pressure and signs of acute target organ injury. The goal is to lower mean arterial pressure by 20-25% within minutes to hours using intravenous antihypertensive drugs like sodium nitroprusside. Hypertensive urgencies also involve severely high blood pressure but without acute organ injury, allowing for oral drugs to safely lower blood pressure within 24 hours. Rapid blood pressure reduction is avoided to prevent hypotension in both conditions.