c# - Difference between IEnumeration instead and List?

You mean IEnumerable. It's the base interface of all collection types like arrays or generic List.

You can for example create a List:

List ints = new List(){ 1,2,3 };

But since it implements IEnumerable you could also declare it in this way:

IEnumerable ints = new List(){ 1,2,3 };

This has the advantage that you cannot modify ints since Remove comes from ICollection.