Choline is a water-soluble B vitamin. It can be produced in the human body, but natural quantities are often insufficient. Natural sources of choline include egg yolk, legumes, wheat germ, peanuts, and organ meats. Bitartrate is added to the choline to speed up the absorption rate within the body.
Choline is a precursor to acetylcholine, a neurotransmitter (i.e. brain chemical) important for memory; it is also a component of phospholipids which make up cell membranes
Low choline intake has been associated with increased fatty liver and raised homocysteine (raised homocysteine is a risk factor for cardiovascular disease and dementia)
Choline bitartrate is a gentle and bioavailable form of choline, suitable for those with impaired liver function.
Choline contributes to:

Normal homocysteine metabolism
Normal lipid metabolism
The maintenance of normal liver function