Sciatica is generally referred to as pain radiating in the lower extremity or lower extremities.  It is generally form irritation of the lower lumbar or upper sacral nerve roots which supply the lower leg and when pinched because of a herniated disc or arthritis related bone spur, the symptoms of pain with numbness and tingling or weakness are radiated down into the leg.

Primary treatment consists of anti-inflammatory medications, resting, and occasionally stretching of the spine such as with physical therapy and traction.  If the supportive treatment does not work in that case further evaluation with x-ray and MRIs and appropriate injections or surgery can help relieve the symptoms.
 
Further information can be obtained from the website links provided.