What is “OfType” in linq?

public void TypeofExa()
{
    Var numbers = {null,1.0,"two", 3,"four",5,"six",7.0 };

    var doubles = from n in numbers where n is doublen;

    Console.WriteLine("Numbers stored as doubles:");

    foreach (object d in doubles)
    {

        Console.WriteLine(d);
    }
}

Output:
Numbers stored as doubles:
1
7