Levels in Unity

This is a very noob question but how do you save different levels off in Unity. I was creating a gui but couldn’t understand where it was calling to and where it gets specified within unity. For instance within the code bit below, where would the 1 be pointing two? Am I suppose to specify this somewhere within Unity or is this calling out to external files? Mostly I just want to know where the 1 points to in this code bit so that I know how to utilize it within the gui.

if (GUI.Button (Rect (70,40,80,20), "Start")){
	Application.LoadLevel (1);
}

I'm not sure to understand your question well...Are you wondering about the origin of that "1" in "Application.LoadLevel (1);"?

In that case, you are calling the loading of a level by its index. And, to do so, you have to go in File->Build Settings to "load" your level into the project build and assign an index to it.

You can also call the loading of a level by its name:

Application.LoadLevel ("Level_1");

, as an example.