"Sagittal images show very mild Grade 1 retrolisthesis of L5 on S!."
This means the bottom vertebrae in your spine has been pushed back out of position. with a lack of moisture in the disk at this level.
"At L4-L5, there is mild annular bulging of the disc with a focal disk protrusion directed toward the left foramen creating mild left foraminal stenosis. There is mild vertabral canal stenosis. There is minimal right foraminal stenosis. The zygapophyseal joints are unremarkable."
At this level a bulge in the disk is narrowing the left foramin. The foramin are grooves in the vertebra that the nerves flow through. The spinal canal at this level is also narrow along with the right foramin. the small pair of joints at the rear of the vertebrae are normal.
"At L5-S1, there is broad based disc bulging directed toward the left foramen. This creates mild vertebral canal stenosis with moderate left foraminal stenosis. There is mild right foraminal stenosis. The zygapophyseal joints are unremarkable."
A bulge in the disk at this level is narrowing the left foramin. There is also narrowing of the right foramin. the facet joints are normal.