What is the 2nd param of BABYLON.GUI.Button.CreateSimpleButton("but", ?) called?

Questions
1

Hi,
If I make a new button:
var niceButton = BABYLON.GUI.Button.CreateSimpleButton(
“such_a_nice_button” , “click me”
);

I can return the name value “such_a_nice_button” on click with:
topicButton.onPointerDownObservable.add(function() {
console.log(niceButton.name);
});

but how can I console.log the “click me”? What is this second (optional) parameter called?

2

There is a getter for the text:
niceButton.textBlock.text

3

Thank you!