It is a movement disorder that causes involuntary spasms in the muscles of the body. It can be generalised affecting the whole body or focal affecting specific parts eg writers cramp, blepharospasm.
Hope this helps.
I am no doctor, but I was diagnosed with TB. I took a medicine for 6 months. You will always have the bug, but chest xrays will show that the bugs are dead! I was diagnosed in 1991...