Please help! what is the difference between a facet block and an epidural injection for back pain relief?

A facet block: Is an injection outside of the spinal canal, on the back/dorsal side of the vertebrae, where as epidural injections go to the space just above the spinal cord. I found some diagrams that might help if you go the site below: http://www.Painmanagementlasvegas.Com/whats-the-difference-between-facet-injections-and-epidural-steroid-injections.Html.

Different: Facet joints are places on the spinal bones where two bones actually meet and articulate, therefore a facet joint injection is into that place where they meet. Many times arthritis or inflammation can arise here and cause pain. Epidural injections are into the spinal canal area or around the spinal nerve roots exiting the spine.