Basically it means: Cast/Convert an array of chars into an enumerable array of strings.
IEnumerable is a collection class which is the base class for almost all the collection classes. In other words, almost all collection classes inherit functionalities from IEnumerable class.
One of the thing that IEnumerable class provides is that you can use foreach loop to iterate over all the elements in an array or list or any other collection that inherits from IEnumerable.
Anyway, I just tested the above code and it doesn't even work. The exception is thrown in runtime saying the it is not able to cast from char to string.
But the above explanation of IEnumerable class is still correct :-)