Consider taking 4 objects out of 11 objects.
1st choice is any object out of 11. So there are 11 choices.
2nd choice is any object out of 10. Combine these two choices: 11×10.
3rd choice is any object out of 9: combine the choices so far: 11×10×9.
Final choice is any object out of 8. Combination: 11×10×9×8=7920.
But if the objects can be selected in any order we must reduce 7920 by the number of ways of 4 objects can be ordered. There are 24 ways to order 4 objects so the number of combinations is 7920/24=330.