Coroutine's yield differences.

I’m confused with the following:

yield return null;
yield return 0;
yield return true;
yield return false;

Are they all the same? Can someone help me understand the differences of each? I know there are a lot of coroutine questions already but I think this is a specific one. Thanks for the help!

PS: This is in C# BTW.

Here Read this May it can help

as Your Yeild True And False

while( !myBoolTrue )
{
    yield return null; // can return any Veriable or Integers Like 0,1,2 etc
}