The difference between a permutation and a combination is regarding if the selection of order matters or not. A permutation is an arrangement of objects in a specific order (how many different arrangements you can make). An example of this could be voting for officers for the school PTO. If there are 10 members and you need to vote on a president, vice president, and a secretary order matters because the president cannot also be the vice president or the secretary. On the other hand, if you go to an event to support the PTO and they are selling snacks to raise money and you can pick 2 different snack out of 6 snack choices, you would use a combination formula because the order of the 2 snacks doesn't matter. There is no reason to debate on if you should get popcorn and a candy bar OR a candy bar and popcorn, it is the same thing