Explain about IEnumerable..??

Question

Please explain about IEnumerable in easy way and why we need?

 

List<int> Yrs = new List<int>();

Yrs.Add(1992);

Yrs.Add(1993);

Yrs.Add(1994);

Yrs.Add(1996);

Yrs.Add(1997);

Yrs.Add(1998);

// IEnumerable<int> ienum = (IEnumerable<int>)Yrs;

foreach (int i in Yrs)

{

Console.WriteLine(i);

}

 

With out IEnumerable also foreach loop works what is the need?