What is the difference between buldging disks and herniated disks?

Synonyms. The terms bulging disk, slipped disk, herniated disk are roughly the same idea that they disc has moved out of place where it should be and possibly compressing nerve or spinal cord. Typically though herniated disk signifies a slight increase in severity of pathology over a bulging disc. It gets a little more specific if terms like disc protrusion and disc extrusion come into the mix.
Size. Bulging discs are normal findings on imaging studies while disc herniations are discs that have moved out of there normal position.