C# – Can someone please show me a very simple example of Interfaces [closed]

interface IFlyable
{
    void Fly();
}

class Bird : IFlyable
{
    public void Fly() { }
}

class Plane : IFlyable
{
    public void Fly() { }
}

List<IFlyable> things = GetBirdInstancesAndPlaneInstancesMixed();
foreach(IFlyable item in things)
{
   item.Fly();
}

Bird and Plane have no common base class except Object, but you can see using the same interface we can deal with them grouply in our program, because they have the same “feature”: Fly.