Q.Why f-block elements are called inner transition metals?

The lanthanoids (La to Lu, Z 57-71) have the general configuration [Xe] 4f0-14 5d0-2 6s2, with the number of 4f electrons varying gradually from 0 to 14 across the series while 6s stays fixed at 2. Because 4f and 5d are extremely close in energy, several elements depart from the simple, naively-expected filling order for the same extra-stability reason used throughout d-block chemistry (e.g. chromium/copper): lanthanum takes [Xe]6s2 5d1 rather than 4f1 (4f sits slightly higher for La specifically); gadolinium takes an extra 5d1 electron ([Xe]4f7 5d1 6s2) specifically to leave its 4f subshell exactly HALF-FILLED (4f7) rather than the expected 4f8; and lutetium likewise takes an extra 5d1 electron ([Xe]4f14 5d1 6s2) to leave its 4f subshell exactly COMPLETELY FILLED (4f14). The identical logic recurs in the actinoid series for curium (5f7 6d1, half-filled 5f7) and lawrencium (5f14 6d1, fully-filled 5f14) -- both are the actinoid-series parallels of gadolinium and lutetium respectively.