First, I am not a doctor nor do I have a radiology background, so am only giving information from my own knowledge base. Your doctor should explain your scan results to you in detail.

Basically it says your back is fine down to the base of your lumbar area/top of your tail-bone area, but at this level you have what some call a 'slipped-disk'.

Each of our vertebrae have their own name and number according to their area in the spine. For example, L1 means the first spinal bone in the lumbar region.

When the numbers quoted are between two vertebrae. eg. L1/L2, it's actually the space between the bones, or the disks that are being discussed.

L5/S1 refers to the disk between the last (or 5th) Lumbar vertebrae and the first Sacral one.

Between each bone in our back (vertebra) we have thick disks filled with gel which act as shock-absorbers, and those disks in turn are covered with a thick material called the annulus (annulus means 'around the outside').

Over the years these disks start to wear out and flatten, or possibly bulge out (like squashing a marshmallow) which is what has happened to you in your L5/S1 area.

With conditions of this type you'd probably find physio beneficial in easing the low back pain that I'm sure you have.

I hope that's helped and if you need any further information, there are some good web sites that help you understand your own reports.

Here's one I found fairly easy to follow..
http://www.radiologyassistant.nl/en/4556dea65db62