Good design disappears from the user's point of view

It's very complex to make something simple, by whittling away and reducing until you are left with the essence of the problem being solved. When it is achieved, the technology just "fades away" and you are no longer aware of the tool. It's just an extension of yourself.

One of the things I love about the iPad, for instance, is when you’re using the iPad, the iPad disappears, it goes away. You’re reading a book. You’re viewing a website, you’re touching a web site. That’s amazing and that’s what SMS is for me. The technology goes away and with Twitter the technology goes away. It’s so easy to follow anything you’re interested in. It’s so easy to tweet from wherever you are. And the same is true with Square. We want the technology to fade away so that you can focus on enjoying the cappuccino that you just purchased.
— Jack Dorsey

As tools get better, they reduce the amount of stuff you need to learn to use them. Moving towards automatic transmissions in cars removed the need for a clutch, for the shifter, and most importantly, it eliminated need to understand that the car had various gears at all. The car is just magic.

You shouldn't need to learn about computers in order to use them.