Public Parking
This sign means that there is public parking available.
Public means that anyone can use the parking spaces. The parking might be free or drivers might have to pay a fee.
Taxi Zone
The area next to the curb is for taxicabs only.
Don't park in a taxi zone.
No U Turn
This sign means that drivers cannot make a U-turn.
Some states only allow drivers to make a U-turn at traffic signals if there is a sign that says they can. Check the DMV handbook in your state.