Mars (also Mars bar) is a chocolate bar manufactured by Mars, Incorporated. It was first manufactured in Slough, Berkshire in the United Kingdom in 1932 as a sweeter version of the American Milky Way bar which Mars, Inc. produced in the USA (not to be confused with the European version of Milky Way, which is a different confection and similar to the US 3 Musketeers). It was advertised to the trade as being made with Cadbury’s chocolate as ‘couverture’.
In the United States, a different confection bears the Mars bar name. Featuring nougat, soft caramel, and almonds coated in milk chocolate, the American Mars bar was relaunched in 2010 after being discontinued in 2002.
Info gleaned from Wikipedia