The query that is often asked - what is sciatica? The answer is that sciatica is the pain that starts in the lower back and radiates down one of our legs. This specific condition has become quite a common complaint and is caused by pressure on the sciatic nerve which runs down into our legs. In medical term, it is called acute nerve root compression. This is part of the issues that are faced by lots of people when it comes to experiencing back pain and so the learning of sciatica is a crucial piece of information to learn.