Refresher on contacts and pisto grip switches

[dm9289]

I look at many old diagrams that have pistol grip 3 position rotary switches or contact block diagrams with the asterisk * showing what contacts are in each state depending on the switch position.

I always get confused if a contact is nc and if the switch is changed to the asterisk position what happens if it opens or what.

Long and short I have been searching the web for a quick refresher course so I dont have to take the device apart and figure it out each time. I see these old diagrams often so this would be very helpful if someone could suggest a reference?

Thanks
Dave