So what EXACTLY are TRANS FATS and how are they formed?

Question

Some overseas supermarkets are banning it from their shelves.

Answer 1

What is Trans Fat?
Where will I find trans fat?
Vegetable shortenings, some margarines, crackers, cookies, snack foods, and other foods made with or fried in partially hydrogenated oils.Unlike other fats, the majority of trans fat is formed when liquid oils are made into solid fats like shortening and hard margarine. However, a small amount of trans fat is found naturally, primarily in some animal-based foods. Essentially, trans fat is made when hydrogen is added to vegetable oil -- a process called hydrogenation. Hydrogenation increases the shelf life and flavor stability of foods containing these fats.
http://www.cfsan.fda.gov/~dms/transfat.html

http://www.bantransfats.com/abouttransfat.html

Answer 2

Trans fatty acids (commonly termed trans fats) are a type of unsaturated fat (and may be monounsaturated or polyunsaturated).

Trans fats occur naturally, in small quantities, in meat and dairy products from ruminants. Most trans fats consumed today, however, are industrially created through partial hydrogenation of plant oils and animal fats — a chemical process developed in the early 1900s and first commercialized as Crisco in 1909. Unlike other fats, trans fats are neither required nor beneficial for health.[1] Eating trans fat increases the risk of coronary heart disease.[2] For these reasons, health authorities worldwide recommend that consumption of trans fat be reduced to trace amounts. Trans fats from partially hydrogenated oils are generally considered to be worse than those occurring naturally.[3]