A disc herniation is a bulge of the disc.
The position of the disc bulge/herniation and its impact on the spinal cord or nerve
root that is important. Think of the disc as a tube of toothpaste with a hole, the tube as the annulus or outside of the disc and the paste as the nucleus, the inside of the disc. With a hole in the tube the paste begin to ooze out just like the disc nucleus.