In a hospital setting, the attending physician or "attending" is the primary care physician for any single patient. An attending has completed a residency in a medical speciality and practices in that specialty. They are responsible for, and they are the only ones entitled to make, care decisions with respect to the patient. Other physicians may work with the patient, such as fellows, residents, interns and even medical students, and the attending may consult with other specialists, but the final welfare of the patient and the result achieved, positive or negative, is attributed to the attending physician.
Generally speaking, the attending stays on the case unless they are dismissed by the patient or reassigned by the head of medicine. However, at that point, a new attending physician must be assigned.
Subordinates and specialists working under the direction of the attending physician are required to perform the tasks assigned to them, even if they disagree with the attending. For example, in the episode Distractions, the anesthesiologist disagreed with House's decision to wake a burn patient, but House "pulled rank" on him even though the specialist was not under House's supervision and House himself did not have the skills that the anesthesiologist had.
Similarly, the attending is often blamed for mistakes made by their subordinates. For example, in The Mistake, House was the attending physician for the patient and was disciplined when Chase made a critical mistake that cost the patient her liver.