Why there is a squeaking noise when I'm driving but stops when I hit the brakes?

The squeaking noise could be caused most likely due to your brake pads. When you hit the brakes, the pads press against the rotors and stop the wheels from turning. Over time, the brake pads can wear down and become thinner. This can cause them to squeak when they press against the rotors. You may need to have your pads replaced if they are worn down too much.