A bulging disc is very similar to a herniated disc. Technically, the definition differs according to the American Society of Neuroradiologists. But the distinction is not really important, clinically. The distinction is an anatomical/morphological one. From the patient’s standpoint, the distinction is not really important, since both can be painful.
Generally, herniations are worse than bulges. Herniations are more likely to put pressure on a nerve root and be a significant source of spinal pain and radiating pain down the arm or leg. Disc bulges are generally more diffuse, meaning they bulge out beyond the vertebral borders over a broader expanse than a herniation, which is more focal. But the importance of the bulge is whether or not it is a source of pain and/or puts pressure on a nerve. Bulges are sometimes not symptomatic.
Generally bulges and herniations are most common at the lowermost part of the back and less common at subsequently higher levels of the lower back. Therefore, they are most common at L5-S1. And they are least common at L1-L2. Just like herniations, they seldom require injections or surgery as a means of treatment. And just like herniations, spinal decompression treatment has, in my experience, been the most effective means of treatment. Spinal decompression works by pulling the vertebrae apart to lower the pressure in the disc and encourage the disc contents to migrate back from where they came. This gets the pressure off of the outer fibers of the disc, which can be a source of pain, as well as off of the nerve root, if the nerve is being pinched. On occasion, the joint is also a source of pain and this, too, is alleviated by decompressing the spine.
It should be noted that the vast majority of surgical treatments, i.e. about 98%, are done for the purposes of decompressing the spine. This is true for disc surgeries as well as fusions, as well as stenosis-related surgery. It is implicit, in these common surgical procedures, that compression is the cause of pain, and decompressing the lesion is the cure for the pain. This is exactly why my method of spinal decompression is the most effective, nonsurgical treatment- because it treats the actual cause of the pain. Other treatments, such as physical therapy, chiropractic and exercises including core strengthening, do not treat this cause of pain. As a result, these treatments are much less effective for patients, hence many more patients will get injections and surgical treatment, because their nonsurgical treatment is less effective.