Essential tremor (ET, also referred to as benign tremor, familial tremor, or idiopathic tremor) is a progressive neurological disorder that is also the most common movement disorder. The cause of the condition is currently unknown.

Source : Wikipedia

Unlike Parkinson's diseaseplugin-autotooltip__plain plugin-autotooltip_bigParkinson's disease

Also known as Parkinson disease, Parkinson's, idiopathic Parkinsonism, primary Parkinsonism, PD, or paralysis agitans - is a degenerative disorder of the central nervous system resulting from the death of dopamine-containing cells in the the tremors occur when the patient is trying to perform a movement, rather than when at rest.

In about half of cases, the disease has been associated with genetic abnormalities, though no genes have yet been identified. It's generally presumed that environmental factors may also contribute.

A 2014 study found abnormally high levels of a protein called LINGO1 in the brains of ET patients. It's currently not known if the excess protein is a cause of ET or a result of it.

See : Movement Disorders , Volume 29, Issue 13, pp. 1637-1647