IEnumerable is an interface, implemented by System.Collecetion type in .Net that provides iterator pattern. The definition according to MSDN is:

"Exposes the enumerator, which supports simple iteration over non-generic collection."

It's something that you can loop over. That might be a List or Array or anything else that supports foreach loop.

IEnumerator allows you to iterate over List or array, and processes each element one by one