In the Arduino Uno's basic manual, connections for fading led are given. They have connected led on breadboard. The positive of led is connected through a resistor to the pin no 9 (pwm) and negative to the ground (ground of arduino with a wire). There is also a connection of 5V from arduino to breadboard. The led worked fine without that connection too. Is there any use to it? (It is given in the manual)
There is no need for the 5V pin to be connected to the breadboard, maybe this setup is part of a tutorial and 5V will be used in a later part.
It serves no purpose. Pin 9 can provide enough current to power and dim a single led.