There's an old saying that elephants never forget (what do they have to remember?).
This Project is like an Elephant ... it never forgets either! (But it doesn't eat peanuts...)
When you finish the wiring connections, you'll notice that LED 1 is lit. Set the Select Switch at B and press the Key. LED 1 will go out, but will light again when you release the Key.
Now set the Select Switch to A and press the Key. What happens when you release the Key?
Now set the Select Switch back to B and see what happens.
While you've got the Select Switch at B, try this: press the Key so LED 1 goes out, Keep holding the Key down so LED 1 stays dark and set the Select Switch to A. Release the Key. What happens?
Try pressing the Key a few times to see if there's any change. This Project is an example of a latching circuit. When you press the Key with the Select Switch at A, the LED will go out and will not light again no matter how much you press the Key. We say this circuit memorizes the LED "off" state at A.
You also found that if you had LED 1 out at B and then set the Select Switch to A that the LED would stay out even when you released the Key.
You may have heard people refer to a computers ''memory" Information is stored in a computer by electronic circuits. In early computers relay circuits such as this were used to store information!