Electrical properties of keyboard keys
Keyboard keys conduct electricity when you press them down so you want normally open momentary press switch. To find where a button that you press is (for instance the letter "C", try to follow the lines where the switch goes and then check for electrical conductance with a multimeter (or a battery with an LED) when you press the button down. When you press it, the resistance of the leads should go from infinite ohms to close to 0 ohms.