Step 1: Recall kidney gross anatomy.
Each kidney is bean shaped, with a convex outer border and a concave inner border.
Step 2: Locate the point of entry and exit.
The renal artery, renal vein, nerves, and the ureter all pass through a single notch on the concave inner border of the kidney.
Step 3: Name the structure.
This specific notch is called the hilum (or hilus). The pelvis and calyces are internal chambers that collect urine, and the ureter is the tube carrying urine away, so none of these describe the notch itself.
\[ \boxed{\text{Hilum}} \]