Not sure if people explained the main principle properly. The key position every pin at the same time into the correct position to allow the lock to open. If all the pins were perfectly made there wouldnt be other ways to unlock it.

But they arent. They wont be. They cant be. And you can use this to position each of the pins into correct position one at a time. This is why you have the turning tool that you apply pressure to to make the pins press into the sides of their holes. At any given moment, due to the imperfection, only one will be pressed against the walls completely.

Once you position that first pin, the lock will turn ever so slightly and another pin will now be the one that is pressed. Do that for all pins and the lock will eventually turn open. All that is left is to find the correct order of pins being pressed into the side of the cylinder.

The pin that is pressed is the one that is "binding". When there is "nothing" on a pin, it means its not being pressed at all. When pin that was binding "clicks" it means it has been set into the right position, which made the cylinder rotate and now a new pin is "binding".