There's many different ways to describe a disc problem. Some people have heard of the term a disc bulge, some people have heard of the term slipped discs, some people have heard the term a herniated disc, there's also the term degenerative disc disease.
A disk is a type of material. It's a soft, rubber band-like substance that is sandwiched between the bones of the spine. The bones of the spine then have a soft, gelatinous, rubber band-ish type material called a disc between them, so when you jump up and down, the bones don't hit each other and break. It is a shock absorber, it's a ligament, it holds the bones on top of each other, and it also acts as a spacer. That space is necessary to spread the bones apart from each other to allow the nerves to come out from the middle of the spine into the arms and legs. So the disc is a very, very important structure.
But, the discs do wear out over time.
What we do know is, when you are born, that's probably the only time your discs are relatively normal. They're full of water, they're normal in shape, they're normal in size, they do their function. As time goes on, the discs start to degenerate, and the degenerative process so something called the degenerative cascade.
Most people believe what happens is the chemicals inside the disc, some of the chemicals are called proteoglycans, change their makeup and it no longer can hold the water in the center of the disc like it did when you were younger. So the water starts to seep out of the disc, and when the water starts to seep out of the disc, that's when you start developing these things called slipped discs or bulged discs or herniated discs.