Most people just take what they read or what they were taught without giving it much thought.
For the everyday road user, the blue colour "U-turn" sign means they can do a 180 degree turn to drive towards the opposite side of which they are facing.
However, the term "U-turn" is technically incorrect.
Look at the shape of the U relative to the direction which the driver desires to go..
Technically and diagrammatically, it should be known as the "n-turn"..