Can you please give me a technical description of sciatica, and is it bad?

Nerve pressure pain: Sciatica is layman's term for leg pain from a pinched nerve in the back. 'bad' is a relative term, depending on cause, intensity and associated symptoms.

Pyriformis v disc: Can be due to disc herniation in back or to hip muscle-pyriformis irritating sciatic nerve which it straddles in the buttock region mimicking herniation pattern. Intrapelvic lesions and lesions of sciatic nerve can cause symptoms. Late lyme disease can cause this pain pattern, spondylolysis/ listhesis, spinal stenosis or synovial cyst or other mass in spine. If from a disc, 90% get better nonop.

See below: A set of symptoms including pain that may be caused by general compression or irritation of one of five spinal nerve roots that give rise to each sciatic nerve, or by compression or irritation of the left or right or both sciatic nerves. Symptoms include lower back pain, buttock pain, and pain, numbness or weakness in various parts of the leg and foot.

Back & Leg Pain: Sciatica is pain in the distribution of the leg as a result of an irritated nerve or facet joints or other injury typically in the lumbar spine (low back) which are caused by herniated disks, spinal stenosis or degenerative disc disease, etc requiring further evaluation by a spine specialist and may be candidate for facet injections/radiofrequency ablation and epidural steroid injection.