Mr. Hallkids

Hi Scotty,
my wife got a free car from her mother. With 145000 miles on its. Honestly, her mother never really took care of the car and had it for 9 years and it’s still running lol. Her mother informed me that when you put the car Reverse the rears brakes makes a grinding noise. What are the car does that mean the brakes are locked or need to be changed ? I believe they need to be changed. And I do not know how to do drum brakes can you show me ? Lol