does using IEnumerable interface reduce concurrency issues
===

According to Albahari brothers,`IEnumerable` is used because

->iteration logic can be `framed off to another class`(**Understood**)

->`several consumers can enumerate the collection at once without interfering with each other`(**Not understood**)

I am not able to understand the second point!

How can `IEnumerable` instead of using `IEnumerator` enable **multiple consumers to enumerate the collection at once**?