A disc herniation is a portion of a disc outside its normal confines while a sciatica
is a radiculopathy
which is pain over a nerve
path caused by an irritation, pinching or compression
of that nerve which could include a disc herniation, a cyst, a tumor or mass, a blood clot
called a hematoma or spinal stenosis
to name a few in the spine but there are also causes in the pelvis ;/or leg.