Ashkenazi and Sephardi Jews lived in different parts of the world with different food staples. The rules are only different during Passover and even then, the differences are minor.
Generally speaking, Ashkenazi laws of kashrut are stricter.
Judaism. See also:http://judaism.answers.com/jewish-laws/laws-of-keeping-kosher
Kosher is not a company, but rather a set of Jewish dietary laws. The label "kosher" is applied to any food which is manufactured in accordance with these laws.
Everything is specific on how kosher foods are prepared.
Kosher Laws
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In order to make kosher gourmet bread, all of the ingredients would have to be certified kosher and the bread itself must be prepared in a kosher kitchen following the laws of kashrut (Jewish dietary laws).
Partridge is a kosher bird but has to be slaughtered and prepared following the laws of kashrut.
The actual word is 'kosher', not 'kosha'. Kosher refers to food that is prepared following the laws of kashrut (Jewish dietary laws). A kosher kitchen is a kitchen that is set up so that it meets the requirements to produce kosher food.
Kosher means fit. The set of laws about what makes food kosher is called 'kashrut'. These laws specify what foods religiously observant Jews can and cannot eat.
Any cheeses made from kosher ingredients by a manufacturer that is certified kosher is kosher. Kosher refers to any food prepared according to the laws of kashrut (Jewish dietary laws), it is not a style of food.
Kosher soup is any soup that is made following the laws of kashrut (Jewish dietary laws). It is not a specific type of soup.