The difference between a herniated and bulging disc are simple. To use a common metaphor among physicians, think of a disc like a jelly donut. The donut has a liquid center surrounded by a thicker shell. If you press down on the donut, the sides bulge out as the jelly inside presses against them – this is a bulging disc or disc protrusion. If you press down on the donut hard enough that the jelly comes out, it becomes a herniated disc, ruptured disc, or torn disc.
The term “slipped disc” is a kind of slang for accepted medical terms that relate to disc disorders that rarely include slipping. The term has become popular in non-medical articles and social media posts, but disc slippage is rarely, if ever, involved. More often than not this phrase actually refers to a herniated or bulging disc pushing into nerve endings nearby.