using IEnumerable over List in C#

What's the advantages to use IEnumerable over List? For example I have a Employee class and a collection of employee objects, if I want to iterate each employee, I can either use:

List employees = new List() { new Employee(...),...}
foreach (Employee emp in employees)
{
   Console.WriteLine(emp.Name);
}

or I can use Ienumerable as :

IEnumerable employees = new List() { new Employee(...),...}

then use foreach loop.

Both of them achieve same goal, so why we sometimes prefer to use IEnumerable over List?