The rear is the entire back assembly of the dog: hind legs, hips, feet, everything. Rear is responsible for what is known as "drive." That is, it's the part of the dog that pushes forward. The dog doesn't pull itself along like a front-wheel drive car, it pushes.

Rears with faults indicate a dog that does not have as much drive as it could - inefficient gaits can mean the dog tires easier.