Shock is defined as inadequate arterial circulation to meet tissue metabolic needs. It is classified into four types: hypovolemic, cardiogenic, obstructive, and distributive shock. The diagnosis of shock involves low systolic blood pressure, tachycardia, peripheral vasoconstriction, altered mental status, and metabolic acidosis. Treatment depends on the cause, severity, duration, and underlying patient conditions and involves oxygenation, IV fluids, monitoring, and addressing the primary cause of shock.