What is chronic pars defect w/o Spondylolisthesis

I recently had a ct scan done for kidney stones and saw they noted this in the results. They never even brought this up? I’ve never been made aware of this.

From my understanding I have a small fracture in my L5 and the vertebrae hasn’t shifted?

What are some good exercises/PT to do daily? I am a T2-L2 spinal fusion and try to take care of my back as much as possible