C# - How is a combination of flag values converted to string?

C# - flags.ToString().dib

#!meta

{"kernelInfo":{"defaultKernelName":"csharp","items":[{"aliases":[],"name":"csharp"}]}}

#!csharp

/** Q: How is a combination of flag values converted to string?
    A: 3 is "one, two"
*/
[Flags]
enum Parsely{
    none = 0,
    one = 1,
    two = 2,
}

Parsely parsely = (Parsely)3;
parsely.ToString().Display();