1. You have one switch. Correct?
No, I have one switch and one pushbutton. (see image)
2. At what DPin (digital pin) is the switch connected?
D1 = Push button
D3= Switch
3. Switch is low -- does it mean the switch is closed?
Switch open = Low
Switch closed = High
4. Switch is high -- does it mean the switch is opened?
See point 3
5. Button is pushed -- does it mean that you have another switch named Button? It is pushed -- does it mean that the Button is closed?