Kosher has to do with what G-d says is okay to eat (you can find that in Leviticus 11 versus 1-47), the killing of the animal correctly if meat is involved, the preparation, and of course a Rabbi making sure everything is done proper and certifying that item kosher and the proper symbol being put upon it. What is kosher is not always good for you though....OREOS are kosher, M&Ms are kosher, LAYS potato chips are kosher, and so is COKE, but that doesn't mean I should eat them every chance I get.


All fresh fruits and veggies are kosher so long as they are not cut or prepared. You know how some produce departments will cut up some of their fruits and veggies and then tag and bag them. At that point, depending on your level of kosher you can't buy them because you don't know what their "kitchen" is like.
So much detail and so much more, but not enough time to tell. Hope this helps a little.