What is the difference between permutation and combination?

 

Permutation:

An arrangement of the objects with a specific order is known as permutation. The permutations of n objects taken r at a time are denoted by P(n,r) or nPr . Formula for permutation:     P(n,r)= n!/((n-r)!)

Combination:

The collection /selection of objects taken some or all of them at a time without regarded to order is called Combination. The combination of  n objects taken r at a time is denoted by nCr or C(n,r) Formula for combination C(n,r) = n!/(n-r)!r!

Furthermore, you can see the given pdf file with an example.