Endotracheal intubation involves placing a flexible plastic tube into the trachea to maintain an open airway or administer drugs. It is used to administer oxygen, remove secretions, ventilate the lungs, and treat respiratory failure or hypoxemia. Indications include central nervous system depression, neuromuscular disease, chest wall injury, upper airway obstruction, aspiration prophylaxis, and spinal fractures. The procedure involves positioning the patient, using a laryngoscope to view the vocal cords, inserting the tube, inflating a cuff if present, securing and connecting the tube to a ventilator or Ambu bag.