Apple just announced a new Macbook, boasting that it completely reinvented the keyboard in order to make the laptop as thin as possible.
It comes down to the way each individual key is designed.
Apple created a new "butterfly" mechanism, which more evenly distributes the pressure on a single key than the traditional "scissor" mechanism. That supposedly means a more precise typing experience and less errors. It's thinner because each key actually moves less when you press it.
Overall, the butterfly keyboard is 40% thinner than a scissor keyboard, and four times more stable.
Here's a look at the two different designs:
Apple
There's a stainless steel dome under each key, that Apple says will make typing feel "crisp and responsive":
Apple
Here's another look at how it all fits together:
Apple
Apple has also put a small LED light behind each individual key, so that when you backlight the keyboard, it brightness will look even all over.