1. It associates the Button image with the variable you select. Therefore, if you switch the variables state, it switches the button image to it's "Press" state.

2. If you insert some text, when you press the button, it will display the text you entered.

3. Most likely, that's what you'd use the answer to #1 for.

4. Yes as well. This is a bit more tricky, but not too bad. Again, use the same technique as #1, set up on the button (or whatever) you want to change, then create the button you want to control that change, and alias the first button. Use this in combination with #2, and you can create scrolling labels that give updates as you press buttons. Nice with toggle codes.