IEnumerable is an interface that defines one method GetEnumerator which returns an IEnumeratorinterface,this in turn allows readonly access to a collection.

An IEnumerable is a thing that can be enumerated.which simply means that it has a GetEnumerator method that returns an IEnumerator.

An IEnumerator is a thing that can enumerate: it has the MoveNext, Current, and Reset methods.
Below is snippet code for IEnumerable

IEnumerableobjIenum = (IEnumerable)obj;
foreach (stringstrinobjIenum)
{
MessageBox.Show(str);
}
In the above IEnumerablesnippet code you can read the data.
Below is snipped code for IEnumerator.
IEnumerableobjIenum = (IEnumerable)obj;
foreach (stringstrinobjIenum)
{
IEnumeratorobjEnumerator= objIenum.GetEnumerator();
while (objEnumerator.MoveNext())
{
string s = objEnumerator.Current.ToString();
MessageBox.Show(s);
}
}

In IEnumerator you can use MoveNext,Current, and Reset methods as I have used in above code.

You will be also interested in watching the below video what are generics.

Please click here to see more  .Net interview questions