Magnets!
Since Apple designs both the iPad Pro and the Magic Keyboard, the two naturally fit together like a hand in a glove, and in this case that’s accomplished by putting strong magnets in all of the right places.
Most iPad keyboard cases, like most iPad cases in general, are designed to be left on. Taking your iPad out of the case when you don’t want to use the keyboard is more of a hassle than it’s usually worth, which is why many keyboard cases offer either a detachable keyboard, or the ability to fold the keyboard around behind the iPad to use it in a more traditional tablet style.
This isn’t the case with the Magic Keyboard, which is really more of a stand that’s designed to close around your iPad than it is a traditional case. There’s no need to fold it around behind the iPad because there’s no need to keep the iPad attached to it. The iPad simply lines up to the back of the folio, magnetically snapping on in perfect alignment, and when you want to pick up the iPad to read, sketch, or game, you simply need to apply a bit of force at the bottom edge of the iPad Pro, where the rear cover doesn’t come into contact with it, in order to separate it from the magnets, leaving the Magic Keyboard behind.
To be clear, however, the magnets aren’t weak at all. You can shake the Magic Keyboard around or even hold it upside down and the iPad Pro will remain firmly attached. Like Magic.