check brakes and disc on all four wheels they may be worn.
The disc pads are worn out. The grinding is metal to metal contact of the pad backing plate and the rotor. Have the pads replaced and the rotors turned or replaced whichever is applicable. This is a very dangerous situation and should be repaired ASAP.
Incorrect pad / disc combination. There are specific blends of pads that are designed for disc brakes. Some need more metallic components, and some have less. Try the recommended OEM pads for the vehicle.
The brake pads could be worn out
Shimano BO1S Resin pads
Lots of practice, wear a helmet and pads.
New brakes do not grind. If you replaced the brake pads and resurfaced the rotors you may hear a bit of a sound but it is normal until the pads and rotors wear during normal driving.
what kind of wrench to remove brake pads
Disc brake pads push in. they pinch the rotor
it either has front disc brakes and rear drum or it has front and rear disc bakes. look for a flat disc in the front and back - those are front and rear disc brakes-they take pads. The drum brakes take shoes.
You can get special sprays for fixing scratched on CDs.
the fleshy pads of cartilage between the vertebrae
To extend the life of brake pads