What does mean “?” after variable declaration in C#?

Question

i´ve found a code in c# with the following variable declaration in a class

public class Foo
{
    public int ID { get; set; }
    public int Age { get; set; }
    public string name{ ger; set;}
    public bool? Status { get; set; }
}

What does the '?' means, i've just found answer for operator '??' and '?' is null, but not for variable daclaration