I mean its a different kind of food, because in the supermarket i see it and it looks the same like any other food. What is the difference if you know tell me please thank you.
Kosher food follows the dietary laws in Judaism. There are certain characteristics about animals that make them Kosher, and some that make them not. Fish, for example, have to have fins and scales to be kosher. Land animals have to be killed a certain way to be Kosher. Similarly with birds, if they eat other animals and meat, not "vegetarian", they are Kosher. You can tell if something is Kosher if it has a circle around a "U" or a star around a "K". There are other symbols as well, but these are the easiest to explain.
Kosher food is food that's prepared according to the dietary law of Judism. Most Jews will not intake food that is not kosher. For example: Pork and selfish are not kosher, therefore forbidden.