CloudTec, in simple terms, is the inclusion of trademarked round lugs on the sole of On shoes, that act as independent springs, cushioning your landing and propelling you forwards. They also naturally add support, without adding typical medial support (see below)
Why Are They "Like Running On Clouds"?
NorthernRunner.com customers have confirmed that somehow On have created shoes that cushion, feel comfortable, keep momentum quick and very much feel like barefoot.
How Do They Encourage Your Muscles To Work?
The fact they are independent lugs or clouds on the sole of the shoe, rather than one piece of foam/rubber combination cushioning, means that they will engage depending which part of your foot lands first. For example, if you roll inwards or overpronate, the inside of your foot will hit the ground first and the lugs/clouds there will spring into action, cushioning and supporting that part of your foot as the rest hits the floor.
On Running Shoe Reviews/Info